C Defect Report Support in Clang

C defect report implementation status

This page tracks which C defect reports are implemented within Clang.

The implementation status for defect reports against the C Standard are currently under investigation. Any defect report whose status in Clang is currently unknown will be marked in purple.

The LLVM bug tracker uses the "c", "c99", "c11", "c17", "c23", and "c2y" labels to track known bugs with Clang's language conformance.

Number	Status	Issue title	Available in Clang?
1	C89	Do functions return values by copying?	Yes
2	NAD	Subclause 6.8.3.2: Semantics of #	Unknown
3.1	NAD	Are preprocessing numbers too inclusive?	Unknown
3.2	NAD	Should white space surround macro substitutions?	Unknown
3.3	NAD	Is an empty macro argument a constraint violation?	Unknown
3.4	NAD	Should preprocessing directives be permitted within macro invokations?	Unknown
4	NAD	Are multiple definitions of unused identifiers with external linkage permitted?	Yes
5	NAD	May a conforming implementation define and recognize a pragma which would change the semantics of the language?	Yes
6	C89	It is unclear how the strtoul function behaves when presented with a subject sequence that begins with a minus sign	N/A
7	NAD	Are declarations of the form struct-or-union identifier ; permitted after the identifier tag has already been declared?	Yes
8.1	NAD	Is dead-store elimination permitted near setjmp?	Yes
8.2	NAD	Should volatile functions be added?	Yes
9	C89	Use of typedef names in parameter declarations	No
10	NAD	Is a typedef to an incomplete type legal?	Yes
11.1	C89	When do the types of multiple external declarations get formed into a composite type?	Yes
11.2	C89	Does extern link to a static declaration that is not visible?	Yes
11.3	NAD	Are implicit initializers for tentative array definitions syntactically valid?	Yes
11.4	C89	Does an incomplete array get completed as a tentative definition?	Yes
12	NAD	Is it valid to take the address of a dereferenced void pointer?	Yes
13.1	C89	How does one form the composite type of mixed array and pointer parameter types?	Yes
13.2	NAD	Is compatible properly defined for recursive types?	Yes
13.3	NAD	What is the composite type of an enumeration and an integer?	Yes
13.4	C89	When is a struct type complete?	Yes
13.5	C89	When is the sizeof an enumeration type known?	Yes
14.1	NAD	Is setjmp a macro or a function?	N/A
14.2	C89	How does fscanf("%n") behave on end-of-file?	N/A
15	NAD	What is the promoted type of a plain int bit-field?	Yes
16.1	NAD	Can a tentative definition have an incomplete type initially?	Unknown
16.2	C89	Can you implicitly initialize a union when null pointers have nonzero bit patterns?	Unknown
17.1	C89	Are newlines permitted within macro invocations in preprocessing directives?	Unknown
17.2	C89	Should the absence of function main be explicitly undefined?	Unknown
17.3	C89	Does a constraint violation win over undefined behavior?	Unknown
17.4	NAD	Do numeric escape sequences map from source to execution character sets?	Unknown
17.5	NAD	When are character constants implementation defined?	Unknown
17.6	C89	Are register aggregates permitted?	Unknown
17.7	NAD	What is the scope and uniqueness of size_t?	Unknown
17.8	NAD	What types are compatible with pointer to void?	Unknown
17.9	C89	What is the type of an assignment expression?	Unknown
17.10	NAD	When is the sizeof an object needed?	Unknown
17.11	NAD	Is struct t; struct t; valid?	Unknown
17.12	C89	How do typedefs parse in function prototypes?	Unknown
17.13	NAD	How does register affect compatibility of function parameters?	Unknown
17.14	C89	const void type as a parameter	Unknown
17.15	C89	When do array parameters get converted to pointers?	Unknown
17.16	C89	Are subarrays of arrays distinct objects?	Unknown
17.17	C89	How do you initialize the first member of a union if it has no name?	Unknown
17.18	NAD	Are f() and f(void) compatible?	Unknown
17.19	C89	Are macro expansions ambiguous?	Unknown
17.20	NAD	Is the scope of macro parameters defined in the right place?	Unknown
17.21	NAD	Is translation phase 4 defined unambiguously?	Unknown
17.22	C89	Does the rescan of a macro invocation also perform token pasting?	Unknown
17.23	NAD	How long does blue paint persist on macro names?	Unknown
17.24	C89	Can subclause 7.1.2 be better expressed?	Unknown
17.25	NAD	Should must appear in footnotes?	Unknown
17.26	C89	Are unnamed union members required to be initialized?	Unknown
17.27	NAD	Does the # flag alter zero stripping of %g in fprintf?	N/A
17.28	NAD	Does errno get stored before library functions return?	N/A
17.29	C89	When does conversion failure occur in floating-point fscanf input?	N/A
17.30	C89	Do fseek/fsetpos require values from successful calls to ftell/fgetpos?	N/A
17.31	NAD	Are object sizes always in bytes?	Unknown
17.32	NAD	Are strcmp/strncmp defined when char is signed?	N/A
17.33	NAD	Are strcmp/strncmp defined for strings of differing length?	N/A
17.34	NAD	Is strtok described properly?	N/A
17.35	NAD	When is a physical source line created?	Unknown
17.36	NAD	Is a function returning const void defined?	Unknown
17.37	C89	What is the type of a function call?	Unknown
17.38	C89	What is an iteration control structure or selection control structure?	Unknown
17.39	C89	Are header names tokens outside include directives?	Unknown
18	NAD	How does fscanf behave in the presence of multibyte characters?	N/A
19	NAD	Definition of the term "printing character" and isgraph()	N/A
20	NAD	Is a compiler which allows the Relaxed Ref/Def linkage model to be considered a conforming compiler?	Yes
21	C89	What is the result of: printf("%#.4o", 345);?	N/A
22	C89	What is the result of: strtod("100ergs", &ptr);?	N/A
23	NAD	what is the result of strtod("0.0e99999", &ptr);?	N/A
24	NAD	In subclause 7.10.1.4 The strtod function: What does '"C" locale' mean?	N/A
25	NAD	What is meant by 'representable floating-point value?'	Yes
26	NAD	Can a strictly conforming program contain a string literal with '$' or '@'?	Yes
27	C89	Can there be characters in the character set that are not in the required source character set?	Yes
28	NAD	Do object access rules apply to dynamically allocated objects?	Unknown
29	NAD	Do two types have to have the same tag to be compatible?	No
30	NAD	Can 'sin(DBL_MAX)' result in 'errno' being set to 'EDOM'?	N/A
31	NAD	Can constant expressions overflow?	Yes
32	NAD	Must implementations diagnose extensions to the constant evaluation rules?	No
33	NAD	Conformance questions around 'shall' violations outside of constraints sections	Yes
34.1	C89	Does size information evaporate when a declaration goes out of scope, even for objects with external linkage?	Yes
34.2	NAD	If so, can one then write conflicting declarations in disjoint scopes?	N/A
35.1	NAD	Can one declare an enumeration or struct tag as part of an old-style parameter declaration?	Yes
35.2	NAD	If so, what is the scope of enumeration tags and constants declared in old-style parameter declarations?	Partial Tags declared directly within an identifier list are incorrectly scoped to the prototype rather than to the function body.
36	NAD	May floating-point constants be represented with more precision than implied by its type?	Yes
37	NAD	Questions about multibyte characters and Unicode	Yes
38	NAD	Questions about argument substitution during macro expansion	Yes
39.1	NAD	Must MB_CUR_MAX be one in the "C" locale?	N/A
39.2	NAD	Should setlocale(LC_ALL, NULL) return "C" in the "C" locale?	N/A
40.1	C89	What is the composite type of f(int) and f(const int)?	Unknown
40.2	C89	Is an implementation that fails to equal the value of an environmental limit conforming?	Unknown
40.3	NAD	Is an Environmental Constraint a constraint?	Unknown
40.4	NAD	Should the response to Defect Report #017, Q39 be reconsidered?	Unknown
40.5	NAD	Can a conforming implementation accept long long?	Unknown
40.6	NAD	Can one use offsetof(struct t1, mbr) before struct t1 is completely defined?	Yes
40.7	NAD	Can sizeof be applied to earlier parameter names in a prototype, or to earlier fields in a struct?	Unknown
40.8	NAD	What arithmetic can be performed on a char holding a defined character literal value?	Unknown
40.9	NAD	Should the response to Defect Report #017, Q27 be reconsidered?	Unknown
41	NAD	Do characters defined in 5.2.1 impact 7.3.1?	N/A
42.1	NAD	Does memcpy define a (sub)object?	N/A
42.2	NAD	If so, how big is the object defined by memcpy?	N/A
42.3	NAD	How big is a string object defined by the str* functions?	N/A
43.1	C89	Can NULL be defined as 4-4?	Yes
43.2	NAD	Can an identifier that starts with an underscore be defined as a macro in a source file that includes at least one standard header?	Unknown
44.1	NAD	What does it mean to say that the type of offsetof is size_t?	Yes
44.2	NAD	Must the expansion of a standard header be a strictly conforming program?	N/A
44.3	NAD	Does expanding offsetof result in a non-strictly conforming program?	N/A
44.4	NAD	Can one use offsetof in a strictly conforming program?	N/A
44.5	NAD	Is offsetof the only standard macro that renders a program not strictly conforming?	N/A
45	NAD	Is the behavior of freopen defined when the file is invalid?	N/A
46	NAD	Use of typedef names in parameter declarations	Yes
47	NAD	Questions about declaration conformance	Yes
48	NAD	Clarifications on the abort() function	N/A
49	C89	Can strxfrm() output more characters than were input?	N/A
50	NAD	Do wide string literals implicitly include <stddef.h>?	Yes
51	NAD	Question on pointer arithmetic	Yes
52.1	C89	Should the mktime example use (time_t)-1 instead of -1?	N/A
52.2	C89	Is the index entry for static correct?	N/A
52.3	NAD	Does the C Standard come with a Rationale, as indicated in Footnote 1?	N/A
53	C89	Accessing a pointer to a function with a prototype through a pointer to pointer to function without a prototype	Yes
54	C89	Can the string handling functions have a length of 0?	N/A
55	C89	Signal handler macros should have distinct values	N/A
56	NAD	Floating-point representation precision requirements	Yes
57	NAD	Is there an integral type for every pointer?	Yes
58	NAD	Is there a limit on the number of digits processed by scanf and strtdo?	N/A
59	NAD	Do types have to be completed?	Yes
60	C89	Array initialization from a string literal	Yes
61	NAD	Whitespace in scanf format string	N/A
62	NAD	Can the rename function be defined to fail?	N/A
63	Dup	Floating-point representation precision requirements	Duplicate of 56
64	NAD	Null pointer constants	Yes
65	C89	Questions on locales	N/A
66	NAD	Another question on locales	N/A
67	NAD	Integer and integral type confusion	Yes
68	NAD	'char' and signed vs unsigned integer types	Yes
69	NAD	Questions about the representation of integer types	Yes
70	NAD	Interchangeability of function arguments	Yes
71	C89	Enumerated types	Yes
72	NAD	Definition of object and pointer arithmetic	Unknown
73	NAD	Definition of object and array access	Unknown
74	NAD	Alignment and structure padding	Unknown
75	NAD	Alignment of allocated memory	N/A
76	Open	Pointers to the end of arrays	Not resolved
77	NAD	Stability of addresses	Yes
78	NAD	Uniqueness of addresses	Unknown
79	NAD	Constancy of system library function addresses	N/A
80	C89	Merging of string constants	Yes
81	NAD	Left shift operator	Yes
82	C89	Multiple varargs	Unknown
83	C89	Use of library functions	N/A
84	NAD	Incomplete type in function declaration	Yes
85	C89	Returning from main	Yes
86	NAD	Object-like macros in system headers	Yes
87	NAD	Order of evaluation	Yes
88	NAD	Compatibility of incomplete types	Yes
89	C89	Multiple definitions of macros	Yes
90	NAD	Multibyte characters in formats	N/A
91	NAD	Multibyte encodings	Yes
92	Dup	Partial initialization of strings	Duplicate of 60
93	C89	Reservation of identifiers	Yes
94	NAD	Are constraints on function return the same as assignment?	Yes
95	NAD	Is initialization as constrained as assignment?	Yes
96	NAD	Arrays of incomplete types	Yes
97	Dup	Use of offsetof with an incomplete type	Duplicate of 40
98	NAD	Pre/post increment/decrement of function or incomplete types	Yes
99	NAD	ANSI/ISO C Defect report #rfg6	Unknown
100	Dup	Defect with the return statement	Duplicate of 1
101	C89	Type qualifiers and "as if by assignment"	Yes
102	NAD	Tag redeclaration constraints	Yes
103	NAD	Formal parameters of incomplete type	Yes
104	Dup	Incomplete tag types in a parameter list	Duplicate of 84
105	Dup	Precedence of requirements on compatible types	Duplicate of 17
106	NAD	When can you dereference a void pointer?	Yes
107	NAD	Type requirements of the assert macro parameter	N/A
108	NAD	Can a macro identifier hide a keyword?	Yes
109	NAD	Are undefined values and undefined behavior the same?	Yes
110	Dup	Formal parameters having array-of-non-object types	Duplicate of 47
111	NAD	Conversion of pointer-to-qualified type values to type (void*) values	Yes
112	NAD	Null pointer constants and relational comparisons	Yes
113	NAD	Return expressions in functions declared to return qualified void	Yes
114	NAD	Initialization of multi-dimensional char array objects	Yes
115	NAD	Member declarators as declarators	Yes
116	NAD	Implicit unary & applied to register arrays	Yes
117	NAD	Abstract semantics, sequence points, and expression evaluation	Yes
118	C89	Completion point for enumerated types	Yes
119	NAD	Initialization of multi-dimensional array objects	Yes
120	NAD	Semantics of assignment to (and initialization of) bit-fields	Yes
121	NAD	Conversions of pointer values to integral types	Yes
122	Dup	Conversion/widening of bit-fields	Duplicate of 15
123	NAD	'Type categories' and qualified types	Yes
124	C89	Casts to 'a void type' versus casts to 'the void type'	Yes
125	NAD	Using things declared as 'extern (qualified) void'	Yes
126	NAD	What does 'synonym' mean with respect to typedef names?	Yes
127	Dup	Composite type of an enumerated type and an integral type	Duplicate of 13
128	NAD	Editorial issue relating to tag declarations in type specifiers	Yes
129	NAD	Tags and name spaces	Yes
130	NAD	Guarantees when writing text to a stream	N/A
131	C89	const member qualification and assignment	Yes
132	Dup	Can undefined behavior occur at translation time, or only at run time?	Duplicate of 109
133	NAD	Undefined behavior not previously listed in subclause G2	Yes
134	NAD	What is an 'error number' for strerror?	N/A
135	NAD	Can the size argument to 'fwrite' be zero?	N/A
136	NAD	'mktime' and time gaps	N/A
137	NAD	'printf' and negative floating point values	N/A
138	C89	Is there an allocated storage duration?	Yes
139	C89	Compatibility of complete and incomplete types	Yes
140	NAD	Behavior of 'setvbuf'	N/A
141	NAD	What is the meaning of EOF?	N/A
142	C89	Reservation of macro names	Yes
143	C89	'fopen' modes	N/A
144	C89	Preprocessing of preprocessing directives	Yes
145	C89	Constant expressions	Unknown
146	C89	Nugatory constraint	Yes
147	C89	Sequence points in library functions	Yes
148	NAD	Defining library functions	Yes
149	C89	The term "variable"	Yes
150	C89	Initialization of a char array from a string literal	Yes
151	C89	Behavior of 'printf' and flags	N/A
152	NAD	Can you 'longjmp' out of a signal handler?	N/A
153	Dup	Can 'f()' be considered a call to a function-like macro with one empty argument?	Duplicate of 3
154	NAD	Consistency of implementation-defined values	Yes
155	C89	Zero-sized allocations	N/A
156	C89	Closed streams	N/A
157	C89	Legitimacy of type synonyms	Yes
158	C89	Null pointer conversions	Yes
159	C89	Consistency of the C Standard Defects exist in the way the Standard refers to itself	Yes
160	Open	Reservation of identifiers	Not resolved
161	NAD	Details of reserved symbols	Yes
162	C89	'gmtime' and 'localtime'	N/A
163	C89	Undeclared identifiers	Yes
164	NAD	Bad declarations	Yes
165	C89	Tags and incomplete types	Not resolved
166	Open	Meaning of lvalue	Not resolved
167	Open	Consistency of the C Standard (Defect Report UK 015)	Not resolved
168	Open	Consistency of the C Standard (Defect Report UK 016)	Not resolved
169	NAD	Trigraphs	Yes
170	C89	Operators and punctuators	Not resolved
171	Open	Ranges of integral types	Not resolved
172	Open	Relational and equality operators	Not resolved
173	Open	Line numbers	Not resolved
174	Open	Implicit conversions	Not resolved
175	Open	Correction to Technical Corrigendum 1	Not resolved
176	Open	Diagnostics for #error	Not resolved
177	Open	Preprocessing directives	Not resolved
178	Open	Conformance with array members and allocations	Not resolved
201	NAD	Integer types longer than long	Yes
202	C99	Change return type of certain <fenv.h> functions	N/A
203	C99	C locale conflict with ISO/IEC 9945-2	N/A
204	C99	size_t and ptrdiff_t as a long long type	Yes
205	NAD	New keyword __at_least	Yes
206	NAD	Default argument conversion of float _Complex	Yes
207	C99	Handling of imaginary types	Partial Clang detects use of the _Imaginary keyword but does not otherwise support the type yet.
208	C99	Ambiguity in initialization	Yes
209	C99	Problem implementing INTN_C macros	Partial Clang provides these definitions in a freestanding compilation, but the type of the value produced by UINT8_C and UINT16_C is not the type after integer promotion per C99 7.18.4p3.
210	C99	'fprintf' %a and %A conversions recommended practice	N/A
211	C99	Accuracy of decimal string to/from "binary" (non-decimal) floating-point conversions	Yes
212	NAD	Binding of multibyte conversion state objects	N/A
213	C99	Lacuna in 'mbrtowc'	N/A
214	NAD	'atexit' function registration	N/A
215	C99	Equality operators	Yes
216	C99	Source character encodings	Yes
217	NAD	'asctime' limits	N/A
218	C99	Signs of non-numeric floating point values	Yes
219	NAD	Effective types	Yes
220	C99	Definition of "decimal integer"	N/A
221	NAD	Lacuna in pointer arithmetic	Yes
222	C99	Partially initialized structures	Yes
223	C99	'FP_FAST_FMAF' and 'FP_FAST_FMAL' should be integer constant	N/A
224	C99	fpclassify return is not defined	N/A
225	C99	strtod, strtof and strtold expected form of the subject sequence	N/A
226	NAD	strftime references	N/A
227	NAD	strftime %U, %V, and %W conversion specifiers	N/A
228	C99	wmemcmp declaration in Annex B	N/A
229	C99	localeconv() *_sep_by_space table entries issues	N/A
230	C99	Enumerated type rank	Yes
231	NAD	Semantics of text-line and non-directive	No
232	C99	Typo in Annex I	N/A
233	C99	%g, %G precision specification	N/A
234	C99	Miscellaneous Typos	Yes
235	C99	"C" locale collating behaviour not defined	N/A
236	NAD	The interpretation of type based aliasing rule when applied to union objects or allocated objects	Unknown
237	NAD	Declarations using [static]	No
238	C99	Decriptions of fma() overflow and underflow errors are missing	N/A
239	C99	Annex F nexttoward description is inconsistent with 7.12.11.4 and F.9.8.3	N/A
240	C99	lrint, llrint, lround, llround, and ilogb descriptions are not consistent for unrepresentable results	N/A
241	C99	Make the base standard and Annex F consistent for pow(0, <0)	N/A
242	C99	Make the base standard and Annex F consistent for logb(0)	N/A
243	C99	Make the base standard and Annex F consistent for fmod(), remainder(), and remquo() for a zero divisor	N/A
244	C99	tgamma(zero or negative integer) should be considered a pole error	N/A
245	C99	Missing paragraph numbers	Yes
246	NAD	Completion of declarators	Yes
247	C99	Are values a form of behaviour?	Yes
248	C99	Limits are required for optional types	Yes
249	Dup	Lacuna applying C89:TC1 to C99	Duplicate of 9
250	C99	Non-directives within macro arguments	Yes
251	C99	Are struct fred and union fred the same type?	Yes
252	NAD	Incomplete argument types when calling non-prototyped functions	Yes
253	NAD	"overriding" in designated initializers	Yes
254	NAD	mbtowc and partial characters	N/A
255	NAD	Non-prototyped function calls and argument mismatches	Yes
256	NAD	Multiple inclusion of headers	N/A
257	NAD	Common initial sequences and related issues with unions	Unknown
258	NAD	Ordering of "defined" and macro replacement	Yes
259	NAD	Macro invocations with no arguments	Yes
260	NAD	Indeterminate values and identical representations	Unknown
261	NAD	Constant expressions	Yes
262	C99	Maximum size of bit fields	Yes
263	C99	All-zero bits representations	Yes
264	NAD	Graphic characters	N/A
265	C99	Preprocessor arithmetic	Yes
266	NAD	Overflow of sizeof	Yes
267	C99	Typos in 5.1.2.3, 7.24.4.4.5, 7.24.6.1, 7.24.6.1	Yes
268	C99	Jumps into iteration statements	Yes
269	C99	Lacunae in exact-width integer types	N/A
270	C99	wint_t is not the promoted version of wchar_t	N/A
271	NAD	Lacuna in iswctype and towctrans	N/A
272	C99	Type category	Yes
273	C99	Meaning of __STDC_ISO_10646__	Yes The compiler portion of this DR is implemented in Clang, but the __STDC_ISO_10646__ macro is not defined by Clang; the standard library behavior factors into whether this macro can or cannot be defined.
274	C99	Meaning of "character" in <string.h> functions	N/A
275	C99	Bitwise-OR of nothing	N/A
276	C99	Orientation of perror	N/A
277	NAD	Declarations within iteration statements	No
278	C99	Lacuna in character encodings	Yes
279	C99	Wide character code values for members of the basic character set	Yes
280	NAD	struct tm, member tm_isdst, and mktime() in <time.h>	N/A
281	C99	CLOCKS_PER_SEC should not be a constant expression	N/A
282	C99	Flexible array members & struct padding	Yes
283	C99	Accessing a non-current union member ("type punning")	Unknown
284	NAD	Does <math.h> define INT_MIN and INT_MAX?	N/A
285	C99	Conversion of an imaginary type to _Bool	Partial Clang detects use of the _Imaginary keyword but does not otherwise support the type yet.
286	C99	Correctly rounded and rounding direction/mode	N/A
287	Dup	Floating-point status flags and sequence points	Duplicate of 87
288	NAD	Deficiency on multibyte conversions	N/A
289	C99	Function prototype with [restrict]	Yes
290	C99	FLT_EVAL_METHOD and extra precision and/or range	No
291	C99	Corrections to requirements on inexact floating-point exceptions	Unknown
292	C99	Use of the word variable	Yes
293	C99	Typo in Standard - double complex instead of complex in an example	Yes
294	NAD	Technical question on C99 restrict keyword	Unknown
295	C99	Incomplete types for function parameters	Yes
296	C99	Is exp(INFINITY) overflow? A range error? A divide-by-zero exception? INFINITY without any errors?	N/A
297	C99	May FE_* floating-point exception flags have bits in common?	N/A
298	C99	Validity of constant in unsigned long long range	Partial Clang defines the behavior in this situation by automatically using long long or unsigned long long as the underlying type of the constant; however, Clang fails to diagnose the extension in C89 mode with such constants.
299	C99	Is cabs() a type-generic macro?	N/A
300	NAD	Translation-time expresssion evaluation	Yes
301	NAD	Meaning of FE_* macros in <fenv.h>	Yes
302	C99	6.10.2p5: Adding underscore to portable include file name character set	Yes
303	C99	6.10p2: Breaking up the very long sentence describing preprocessing directive	Yes
304	C99	Clarifying illegal tokens in #if directives	Yes
305	C99	6.10.1p3: Clarifying handling of keywords in #if directives	Yes
306	C99	6.10.3p9: Clarifying that rescanning applies to object-like macros	Yes
307	C99	6.10.3p10: Clarifiying arguments vs. parameters	Yes
308	C99	Clarify that source files et al. need not be "files"	Yes
309	C99	Clarifying trigraph substitution	Yes
310	C99	Add non-corner case example of trigraphs	Yes
311	C99	Definition of variably modified types	Yes
312	C99	Meaning of "known constant size"	Yes
313	NAD	Incomplete arrays of VLAs	Yes
314	NAD	Cross-translation-unit tagged type compatibility	Unknown
315	C99	Implementation-defined bit-field types	Yes
316	NAD	Unprototyped function types	Yes
317	NAD	Function definitions with empty parentheses	Yes
318	C99	(double)0.1f with FLT_EVAL_METHOD being 2	Unknown
319	NAD	printf("%a", 1.0) and trailing zeros	N/A
320	C99	Scope of variably modified type	Yes
321	C99	Wide character code values for members of the basic character set	Yes
322	C99	Problem with TC2 Change #67 (Add perror to the list defining byte input/output functions)	N/A
323	C99	Potential problems with TC2 #34, #35, and #36	N/A
324	C99	Tokenization obscurities	Yes
325	NAD	strerror()	N/A
326	C99	asctime()	N/A
327	C99	Italicize definition of variable length array type, add forward references	Yes
328	C99	String literals in compound literal initialization	Partial Clang properly implements the use of string literals in a compound literal initializer, but fails to diagnose use of a variably-modified type at file scope. DR339 (about variably-modified types) is marked as a duplicate of DR328.
329	C99	Math functions and directed rounding	N/A
330	C99	Externally visible exceptional conditions	N/A
331	NAD	permit FE_DIVBYZERO when errno says EDOM	N/A
332	C99	gets is generally unsafe	N/A
333	C99	Missing Predefined Macro Name	Yes
334	Open	Missing semantics of comparison macros	Not resolved
335	NAD	_Bool bit-fields	Yes
336	C99	What does TMP_MAX actually indicate?	N/A
337	C99	stdio.h macro definition problems	N/A
338	C99	C99 seems to exclude indeterminate value from being an uninitialized register	Yes
339	Dup	Variably modified compound literal	Duplicate of 328
340	C99	Composite types for variable-length arrays	Yes
341	C99	[*] in abstract declarators	Yes
342	Dup	VLAs and conditional expressions	Duplicate of 340
343	C99	Initializing qualified wchar_t arrays	Yes
344	C99	Casts in preprocessor conditional expressions	Yes
345	C99	Where does parameter scope start?	Yes
400	C11	realloc with size zero problems	Unknown
401	C11	"happens before" can not be cyclic	Yes
402	C11	Memory model coherence is not aligned with C++11	Yes
403	C11	malloc() and free() in the memory model	N/A
404	C11	Joke fragment remains in a footnote	Yes
405	C11	The mutex specification	N/A
406	C11	Visible sequences of side effects are redundant	Yes
407	C11	Memory ordering of atomics	Unknown
408	NAD	Should locks provide intra-thread synchronization	N/A
409	C11	f(inf) is inf being a range error	N/A
410	C11	ilogb inconsistent with lrint, lround	N/A
411	C11	Predefined macro values	Yes
412	C11	#elif	Yes
413	NAD	Initialization	Yes
414	C11	Typos in 6.27 Threads <threads.h>	N/A
415	C11	Missing divide by zero entry in Annex J	Yes
416	C11	tss_t destruction unspecified	N/A
417	C11	Annex J not updated with necessary aligned_alloc entries	Yes
418	NAD	Possible defect report: fmod(0.,NaN) and fmod(NaN,infinity)	N/A
419	C11	Generic Functions	Yes
420	NAD	Sytax error in specification of for-statement	Yes
421	NAD	Initialization of atomic_flag	N/A
422	NAD	Initialization of atomic types	N/A
423	C11	Defect Report relative to n1570: underspecification for qualified rvalues	Partial Clang properly handles dropping qualifiers from cast operations, but does not yet handle dropping qualifiers from the function return type.
424	Dup	Underspecification of tss_t	Duplicate of 416
425	NAD	No specification for the access to variables with temporary lifetime	Yes
426	C11	G.5.1: -yv and -x/v are ambiguous	N/A
427	NAD	Function Parameter and Return Value Assignments	Unknown
428	C11	Runtime-constraint issue with sprintf family of routines in Annex K	N/A
429	C11	Should gets_s discard next input line when (s == NULL) ?	N/A
430	C11	getenv_s, maxsize should be allowed to be zero	N/A
431	C11	atomic_compare_exchange: What does it mean to say two structs compare equal?	Unknown
432	C11	Possible defect report: Is 0.0 required to be a representable value?	Yes
433	C11	Issue with constraints for wide character function arguments involving RSIZE_MAX	N/A
434	C11	Possible defect report: Missing constraint w.r.t. Atomic	Yes
435	NAD	Possible defect report: Missing constraint w.r.t. Imaginary	Yes
436	C11	Request for interpretation of C11 6.8.5#6	Yes
437	C11	clock overflow problems	N/A
438	C11	ungetc / ungetwc and file position after discarding push back problems	N/A
439	C11	Issues with the definition of "full expression"	Unknown
440	NAD	Floating-point issues in C11 from PDTS 18661-1 UK review, Issue 1	Unknown
441	C11	Floating-point issues in C11 from PDTS 18661-1 UK review, Issue 2	N/A
442	NAD	Floating-point issues in C11 from PDTS 18661-1 UK review, Issue 3	Unknown
443	NAD	Floating-point issues in C11 from PDTS 18661-1 UK review, Issue 4	Unknown
444	C11	Issues with alignment in C11, part 1	Partial Clang rejects use of an alignment specifier in a compound literal expression.
445	C11	Issues with alignment in C11, part 2	Unknown
446	NAD	Use byte instead of character for memcmp, memcpy	N/A
447	C11	Boolean from complex	Yes
448	C11	What are the semantics of a # non-directive?	Yes
449	NAD	What is the value of TSS_DTOR_ITERATIONS for implementations with no maximum?	N/A
450	C11	tmpnam_s clears s[0] when maxsize > RSIZE_MAX	N/A
451	NAD	Instability of uninitialized automatic variables	Unknown
452	C11	Effective Type in Loop Invariant	Unknown
453	C11	Atomic flag type and operations	N/A
454	NAD	ATOMIC_VAR_INIT (issues 3 and 4)	Yes
455	NAD	ATOMIC_VAR_INIT issue 5	Yes
456	Dup	Compile time definition of UINTN_C(value)	Duplicate of 209
457	C11	The ctime_s function in Annex K defined incorrectly	N/A
458	C11	ATOMIC_XXX_LOCK_FREE macros not constant expressions	N/A
459	C11	atomic_load missing const qualifier	Yes
460	C11	aligned_alloc underspecified	N/A
461	NAD	Problems with references to objects in signal handlers	N/A
462	C11	Clarifying objects accessed in signal handlers	N/A
463	NAD	Left-shifting into the sign bit	Yes
464	C11	Clarifying the Behavior of the #line Directive	Yes
465	C11	Fixing an inconsistency in atomic_is_lock_free	Unknown
466	NAD	Scope of a for loop control declaration	Yes
467	C11	Maximum representable finite description vs math	Unknown
468	C11	strncpy_s clobbers buffer past null	N/A
469	NAD	Lock ownership vs. thread termination	N/A
470	C11	mtx_trylock should be allowed to fail spuriously	N/A
471	C11	Complex math functions cacosh and ctanh	N/A
472	C11	Introduction to complex arithmetic in 7.3.1p3 wrong due to CMPLX	N/A
473	C11	"A range error occurs if x is too large." is misleading	N/A
474	NAD	NOTE 1 Clarification for atomic_compare_exchange	N/A
475	C11	Misleading Atomic library references to atomic types	Yes
476	C11	volatile semantics for lvalues	Unknown
477	C11	nan should take a string argument	N/A
478	NAD	Valid uses of the main function	Yes
479	Dup	Unclear specification of mtx_trylock on non-recursive muteness	Duplicate of 269
480	C11	cnd_wait and cnd_timewait should allow spurious wake-ups	N/A
481	C11	Controlling expression of _Generic primary expression	Clang 3.8
482	NAD	Macro invocation split over many files	Unknown
483	NAD	__LINE__ and __FILE__ in macro replacement list	Yes
484	NAD	invalid characters in strcoll()	N/A
485	C11	Problem with the specification of ATOMIC_VAR_INIT	Yes
486	NAD	Inconsistent specification for arithmetic on atomic objects	Unknown
487	C11	timespec vs. tm	N/A
488	C11	c16rtomb() on wide characters encoded as multiple char16_t	N/A
489	NAD	Integer Constant Expression	Partial Clang inconsistently diagnoses folding a constan expression into an ICE as an extension.
490	NAD	Unwritten Assumptions About if-then	Yes
491	C11	Concern with Keywords that Match Reserved Identifiers	Partial Clang issues a reserved identifier diagnostic when the identifier leads with an underscore followed by a capital letter or double underscores, even if the identifier is used for a macro definition.
492	NAD	Named Child struct-union with no Member	Clang 3.6
493	Dup	Mutex Initialization Underspecified	Duplicate of 469
494	C11	Part 1: Alignment specifier expression evaluation	Yes
495	C11	Part 2: Atomic specifier expression evaluation	Not resolved
496	NAD	offsetof questions	Yes
497	C11	"white-space character" defined in two places	N/A
498	C11	mblen, mbtowc, and wctomb thread-safety	N/A
499	C17	Anonymous structure in union behavior	Yes
500	C17	Ambiguous specification for FLT_EVAL_METHOD	Unknown
501	C17	Can DECIMAL_DIG be larger than necessary?	N/A
502	NAD	Flexible array member in an anonymous struct	Yes
503	NAD	Hexadecimal floating-point and strtod	N/A
1000	C2y	Structure type compatibility with flexible array members	Unknown
1001	C2y	Qualified rvalues from structure or union members	Unknown
1002	C2y	Type qualifiers in [*] in abstract declarators	Unknown
1003	C2y	Linkage between library functions	Unknown
1004	C2y	Linkage between library functions	N/A
1005	C2y	Annex D refers to option removed from UAX#31 in revision 39	Unknown
1006	C2y	atomic_fetch operations and "address types"	Unknown
1007	C2y	Implicitly unsigned bit-fields ambiguity	Unknown
1008	C2y	Bad constraint on attributes with tags	Unknown
1009	C2y	extern thread_local should not be an external definition	Unknown
1010	Open	Termination of the execution with threads	Not resolved
1011	C2y	powr(negative, qNaN)	N/A
1012	Open	Error returns from specific width length modifiers	Not resolved
1013	Open	Ambiguity of "same type"	Not resolved
1015	C2y	Imprecise wording for cnd_t functions	N/A
1016	C2y	Are digit separators allowed in __LINE__?	Unknown
1017	Open	Unspecified timing and synchronization for cnd_t functions	Not resolved
1018	Open	Issue with enum compatibility	Not resolved
1019	C2y	String functions and trailing null inclusion	N/A
1020	C2y	Definition of address constant	Unknown
1021	Open	Integer promotions for enumerations	Not resolved
1022	Open	Void expressions and lvalues	Not resolved
1023	Open	static_assert in structure and union definitions	Not resolved
1024	Open	Redeclaration of standard library typedefs	Not resolved
1024	Review	Redeclaration of standard library typedefs	Review
1026	Open	thrd_t as an array type	Not resolved
1027	Open	Member declaration attributes and composite types	Not resolved
1028	Review	jmp_buf as an incomplete array type	Review
1029	Open	Spelling of __LINE__	Not resolved
1030	Open	Lvalue conversion for generic associations	Not resolved
1031	Open	Generic selection controlling expression lvalue of incomplete non-array type	Not resolved
1032	Open	errno as a bit-field	Not resolved
1033	Review	FILE as a void type	Review
1034	Open	Extra members in div_t types	Not resolved
1035	Open	wctrans_t and wctype_t as nullptr_t	Not resolved
1036	Open	Initializer syntactic requirements	Not resolved
1037	Open	Scopes and noreturn declarations	Not resolved
1038	Open	Issues with float_t and related types	Not resolved
1039	Open	Function type attributes on abstract declarators	Not resolved
1040	Open	Freestanding library issues	Not resolved
1041	Open	Alignment of structure and union members	Not resolved
1042	Open	Attributes on compound literals	Not resolved
1043	Open	Issues with library integer types	Not resolved
1044	Open	Alignment specifier consistency rules	Not resolved
1045	Open	Are VLAs adjusted to pointers variably modified?	Not resolved
1046	Open	Order of arguments to powr	Not resolved
1047	Open	Function call returning void	Not resolved
1048	Open	Mixed [non-]designated initializer behavior	Not resolved
1049	Open	Future language direction of storage-class specifiers	Not resolved
1050	Open	Values of wctrans_t and wctype_t	Not resolved
1051	Open	Standard library integer types wider than intmax_t	Not resolved
1052	Open	Relations between standard library integer types	Not resolved
1053	Open	Conversion of NULL to intptr_t or uintptr_t	Not resolved
1054	Open	Signals from freestanding integer conversion	Not resolved
1055	Open	Incomplete enumerated types in the standard library	Not resolved
1056	Open	WEOF in integer constant expressions	Not resolved
1057	Open	Standard library types as atomic types	Not resolved
1058	Open	Categories of standard library types	Not resolved
1059	Open	<fenv.h> types underspecified	Not resolved
1060	Open	Declaring main with attributes	Not resolved
1061	Open	Variably modified parameters with typeof specifiers	Not resolved
1062	Open	Signaling NaNs in structures, unions, and standard library types	Not resolved
1063	Open	Conversions to signed integer types	Not resolved
1064	Open	__VA_OPT__() hypothetical substitution	Not resolved
1065	Open	More issues with noreturn	Not resolved
1066	C2y	Duplicate macro definitions with variadic macros	Unknown
1067	Open	Bitwise operators on signed types	Not resolved
1068	Open	Standard pragmas after labels	Not resolved
1069	Open	Placemarker preprocessing token concatenation and expansion	Not resolved
1070	Open	Evaluation of [static] parameter array lengths	Not resolved
1071	Open	Header names, __has_include, and __has_embed	Not resolved
1072	Open	Initialization with string literals	Not resolved
1073	Open	charN_t in freestanding	Not resolved
1074	Open	Feature test macros and freestanding	Not resolved
1075	Open	Empty structure types as standard library types	Not resolved
1076	Open	Bit-field storage issues	Not resolved
1077	Open	Bit-field expression issues	Not resolved
1078	Open	Valid locations for __VA_ARGS__ and __VA_OPT__	Not resolved
1079	Open	restrict, _Atomic, and multidimensional arrays	Not resolved
1080	Open	_Generic and VLA type compatibility	Not resolved
1081	Open	Limitations on extended integer constant expressions	Not resolved
1082	Open	Dollar signs in nondigits	Not resolved
1083	Open	Whitespace in macro expansions	Not resolved
1084	Open	Unspecified evaluation order of # and ##	Not resolved
1085	Open	Non-finite values in arithmetic constant expressions	Not resolved
1086	Open	Questions about infinity	Not resolved
1087	Open	Reentering variably modified declaration	Not resolved
1088	Open	Objects with temporary lifetime sharing storage	Not resolved
1089	Open	offsetof and va_arg handling of commas outside of parentheses	Not resolved
1090	Open	Pointer arithmetic involving flexible array members	Not resolved
1091	Open	Issues with external definitions	Not resolved
1092	Open	Strictly conforming programs using argv and handling errors	Not resolved
1093	Open	Compatibility of array types completed by initialization	Not resolved
1095	Open	Inconsistent usage of "based on"	Not resolved
1102	Open	Conditions for when types are inferred	Not resolved
1103	Open	Contradictory requirements of linkage	Not resolved
1104	Open	Flexible array members and alignment	Not resolved
1105	Open	Issues with atomic integer types in <stdatomic.h>	Not resolved
1106	Open	Questions about translation limits	Not resolved
1107	Open	decimal_point and thousands_sep issues	Not resolved
1108	Open	grouping and mon_grouping questions	Not resolved
1111	Open	Inconsistent definitions of version macros	Not resolved
1112	Open	Undefined behavior from uninitialized reads	Not resolved
1113	Open	Questions about character constants	Not resolved
1114	Open	Requirements on RSIZE_MAX	Not resolved
1115	Open	Directives partially contained in multiline macro invocations	Not resolved
1116	Open	Requirements on array parameters	Not resolved
1117	Open	Effective type object access requirements	Not resolved
1118	Open	Flexible array member layout	Not resolved
1119	Open	Meaning of TSS_DTOR_ITERATIONS	Not resolved
1120	Open	Full expressions, declarators, and abstract declarators	Not resolved
1121	Open	Bitwise representation of unsigned integer types	Not resolved
1122	Open	Constraints on string literals and character constants	Not resolved
1123	Open	fopen and restrict qualified parameters	Not resolved