[Clang] Add predefined macros for integer constants (#123514)

This adds predefined macros for integer constants to implement section 7.18.4 of ISO/IEC 9899:1999 in `<stdint.h>` in a safe way:

```
__INT8_C(c)
__INT16_C(c)
__INT32_C(c)
__INT64_C(c)
__INTMAX_C(c)
__UINT8_C(c)
__UINT16_C(c)
__UINT32_C(c)
__UINT64_C(c)
__UINTMAX_C(c)
```

Which improves compatibility with GCC and makes it trivial to implement
section 7.18.4 of ISO/IEC 9899:1999.

Clang defines `__INT<N>_C_SUFFIX__`, `__UINT<N>_C_SUFFIX__`,
`__INTAX_C_SUFFIX__` and `__UINTMAX_C_SUFFIX__`, but these macros are
useless for this purpose.

Let's say, for example, that `__INT64_C_SUFFIX__` expands to `L` or
`LL`. If the user defines them as a macros, the compiler will produce
errors if `INT64_C` is implemented in `<stdint.h>` using
`__INT64_C_SUFFIX__`:

**minimal-test.c:**
```cpp
#if defined(__clang__) & !defined(__INT64_C)
#	pragma clang diagnostic push
#	pragma clang diagnostic ignored "-Wreserved-identifier"
#	define __PSTDC_INT_C_(literal, suffix) literal##suffix
#	define __PSTDC_INT_C(literal, suffix) __PSTDC_INT_C_(literal, suffix)
#	define INT64_C(literal) __PSTDC_INT_C(literal, __INT64_C_SUFFIX__)
#	pragma clang diagnostic pop
#elif defined(__GNUC__)
#	define INT64_C __INT64_C
#endif

typedef __INT64_TYPE__ int64_t;

#define L  "Make Clang produce an error"
#define LL "Make Clang produce an error"

int main(int argc, char **argv)
	{
	(void)argc; (void)argv;
	int64_t v = INT64_C(9223372036854775807);
	(void)v;
	return 0;
	}

```

<img width="697" alt="imagen"
src="https://github.com/user-attachments/assets/6df97af6-7cfd-4cf9-85b7-d7c854509325"
/>

**test.c:**
```cpp
#if defined(__clang__) && !defined(__INT8_C)
#	pragma clang diagnostic push
#	pragma clang diagnostic ignored "-Wreserved-identifier"

#	define __PSTDC_INT_C_(literal, suffix) literal##suffix
#	define __PSTDC_INT_C(literal, suffix) __PSTDC_INT_C_(literal, suffix)

#	define INT8_C(literal)    __PSTDC_INT_C(literal, __INT8_C_SUFFIX__)
#	define INT16_C(literal)   __PSTDC_INT_C(literal, __INT16_C_SUFFIX__)
#	define INT32_C(literal)   __PSTDC_INT_C(literal, __INT32_C_SUFFIX__)
#	define INT64_C(literal)   __PSTDC_INT_C(literal, __INT64_C_SUFFIX__)
#	define INTMAX_C(literal)  __PSTDC_INT_C(literal, __INTMAX_C_SUFFIX__)
#	define UINT8_C(literal)   __PSTDC_INT_C(literal, __UINT8_C_SUFFIX__)
#	define UINT16_C(literal)  __PSTDC_INT_C(literal, __UINT16_C_SUFFIX__)
#	define UINT32_C(literal)  __PSTDC_INT_C(literal, __UINT32_C_SUFFIX__)
#	define UINT64_C(literal)  __PSTDC_INT_C(literal, __UINT64_C_SUFFIX__)
#	define UINTMAX_C(literal) __PSTDC_INT_C(literal, __UINTMAX_C_SUFFIX__)

#	pragma clang diagnostic pop

#else
#	define INT8_C    __INT8_C
#	define INT16_C   __INT16_C
#	define INT32_C   __INT32_C
#	define INT64_C   __INT64_C
#	define INTMAX_C  __INTMAX_C
#	define UINT8_C   __UINT8_C
#	define UINT16_C  __UINT16_C
#	define UINT32_C  __UINT32_C
#	define UINT64_C  __UINT64_C
#	define UINTMAX_C __UINTMAX_C
#endif

typedef __INT8_TYPE__    int8_t;
typedef __INT16_TYPE__   int16_t;
typedef __INT32_TYPE__   int32_t;
typedef __INT64_TYPE__   int64_t;
typedef __INTMAX_TYPE__  intmax_t;
typedef __UINT8_TYPE__   uint8_t;
typedef __UINT16_TYPE__  uint16_t;
typedef __UINT32_TYPE__  uint32_t;
typedef __UINT64_TYPE__  uint64_t;
typedef __UINTMAX_TYPE__ uintmax_t;

#define L   "Make Clang produce an error"
#define LL  "Make Clang produce an error"
#define U   "Make Clang produce an error"
#define UL  "Make Clang produce an error"
#define ULL "Make Clang produce an error"

int main(int argc, char **argv)
	{
	(void)argc; (void)argv;

	int8_t    a = INT8_C   (127);
	int16_t   b = INT16_C  (32767);
	int32_t   c = INT32_C  (2147483647);
	int64_t   d = INT64_C  (9223372036854775807);
	intmax_t  e = INTMAX_C (9223372036854775807);
	uint8_t   f = UINT8_C  (255);
	uint16_t  g = UINT16_C (65535);
	uint32_t  h = UINT32_C (4294967295);
	uint64_t  i = UINT64_C (18446744073709551615);
	uintmax_t j = UINTMAX_C(18446744073709551615);

	(void)a; (void)b; (void)c; (void)d; (void)e;
	(void)f; (void)g; (void)h; (void)i; (void)j;
	return 0;
	}
```

Author: redcode

clang/docs/ReleaseNotes.rst

@@ -479,6 +479,17 @@ Non-comprehensive list of changes in this release
   ``__builtin_elementwise_sub_sat``, ``__builtin_reduce_min`` (For integral element type),
   ``__builtin_reduce_max`` (For integral element type).
 
+- The builtin macros ``__INT8_C``, ``__INT16_C``, ``__INT32_C``, ``__INT64_C``,
+  ``__INTMAX_C``, ``__UINT8_C``, ``__UINT16_C``, ``__UINT32_C``, ``__UINT64_C``
+  and ``__UINTMAX_C`` have been introduced to ease the implementaton of section
+  7.18.4 of ISO/IEC 9899:1999. These macros are also defined by GCC and should
+  be used instead of others that expand and paste the suffixes provided by
+  ``__INT8_C_SUFFIX__``, ``__INT16_C_SUFFIX__``, ``__INT32_C_SUFFIX__``,
+  ``__INT64_C_SUFFIX__``, ``__INTMAX_C_SUFFIX__``, ``__UINT8_C_SUFFIX__``,
+  ``__UINT16_C_SUFFIX__``, ``__UINT32_C_SUFFIX__``, ``__UINT64_C_SUFFIX__`` and
+  ``__UINTMAX_C_SUFFIX__``. Pasting suffixes after the expansion of their
+  respective macros is unsafe, as users can define the suffixes as macros.
+
 - Clang now rejects ``_BitInt`` matrix element types if the bit width is less than ``CHAR_WIDTH`` or
   not a power of two, matching preexisting behaviour for vector types.
 

clang/lib/Frontend/InitPreprocessor.cpp

@@ -253,6 +253,8 @@ static void DefineExactWidthIntType(const LangOptions &LangOpts,
 
   StringRef ConstSuffix(TI.getTypeConstantSuffix(Ty));
   Builder.defineMacro(Prefix + Twine(TypeWidth) + "_C_SUFFIX__", ConstSuffix);
+  Builder.defineMacro(Prefix + Twine(TypeWidth) + "_C(c)",
+                      ConstSuffix.size() ? Twine("c##") + ConstSuffix : "c");
 }
 
 static void DefineExactWidthIntTypeSize(TargetInfo::IntType Ty,
@@ -1164,12 +1166,16 @@ static void InitializePredefinedMacros(const TargetInfo &TI,
 
   DefineType("__INTMAX_TYPE__", TI.getIntMaxType(), Builder);
   DefineFmt(LangOpts, "__INTMAX", TI.getIntMaxType(), TI, Builder);
-  Builder.defineMacro("__INTMAX_C_SUFFIX__",
-                      TI.getTypeConstantSuffix(TI.getIntMaxType()));
+  StringRef ConstSuffix(TI.getTypeConstantSuffix(TI.getIntMaxType()));
+  Builder.defineMacro("__INTMAX_C_SUFFIX__", ConstSuffix);
+  Builder.defineMacro("__INTMAX_C(c)",
+                      ConstSuffix.size() ? Twine("c##") + ConstSuffix : "c");
   DefineType("__UINTMAX_TYPE__", TI.getUIntMaxType(), Builder);
   DefineFmt(LangOpts, "__UINTMAX", TI.getUIntMaxType(), TI, Builder);
-  Builder.defineMacro("__UINTMAX_C_SUFFIX__",
-                      TI.getTypeConstantSuffix(TI.getUIntMaxType()));
+  ConstSuffix = TI.getTypeConstantSuffix(TI.getUIntMaxType());
+  Builder.defineMacro("__UINTMAX_C_SUFFIX__", ConstSuffix);
+  Builder.defineMacro("__UINTMAX_C(c)",
+                      ConstSuffix.size() ? Twine("c##") + ConstSuffix : "c");
   DefineType("__PTRDIFF_TYPE__", TI.getPtrDiffType(LangAS::Default), Builder);
   DefineFmt(LangOpts, "__PTRDIFF", TI.getPtrDiffType(LangAS::Default), TI,
             Builder);

clang/test/Preprocessor/init-aarch64.c

@@ -135,26 +135,31 @@
 // AARCH64_CXX-NEXT: #define __GLIBCXX_BITSIZE_INT_N_0 128
 // AARCH64_CXX-NEXT: #define __GLIBCXX_TYPE_INT_N_0 __int128
 // AARCH64-NEXT: #define __HAVE_FUNCTION_MULTI_VERSIONING 1
+// AARCH64-NEXT: #define __INT16_C(c) c
 // AARCH64-NEXT: #define __INT16_C_SUFFIX__
 // AARCH64-NEXT: #define __INT16_FMTd__ "hd"
 // AARCH64-NEXT: #define __INT16_FMTi__ "hi"
 // AARCH64-NEXT: #define __INT16_MAX__ 32767
 // AARCH64-NEXT: #define __INT16_TYPE__ short
+// AARCH64-NEXT: #define __INT32_C(c) c
 // AARCH64-NEXT: #define __INT32_C_SUFFIX__
 // AARCH64-NEXT: #define __INT32_FMTd__ "d"
 // AARCH64-NEXT: #define __INT32_FMTi__ "i"
 // AARCH64-NEXT: #define __INT32_MAX__ 2147483647
 // AARCH64-NEXT: #define __INT32_TYPE__ int
+// AARCH64-NEXT: #define __INT64_C(c) c##L
 // AARCH64-NEXT: #define __INT64_C_SUFFIX__ L
 // AARCH64-NEXT: #define __INT64_FMTd__ "ld"
 // AARCH64-NEXT: #define __INT64_FMTi__ "li"
 // AARCH64-NEXT: #define __INT64_MAX__ 9223372036854775807L
 // AARCH64-NEXT: #define __INT64_TYPE__ long int
+// AARCH64-NEXT: #define __INT8_C(c) c
 // AARCH64-NEXT: #define __INT8_C_SUFFIX__
 // AARCH64-NEXT: #define __INT8_FMTd__ "hhd"
 // AARCH64-NEXT: #define __INT8_FMTi__ "hhi"
 // AARCH64-NEXT: #define __INT8_MAX__ 127
 // AARCH64-NEXT: #define __INT8_TYPE__ signed char
+// AARCH64-NEXT: #define __INTMAX_C(c) c##L
 // AARCH64-NEXT: #define __INTMAX_C_SUFFIX__ L
 // AARCH64-NEXT: #define __INTMAX_FMTd__ "ld"
 // AARCH64-NEXT: #define __INTMAX_FMTi__ "li"
@@ -287,34 +292,39 @@
 // AARCH64-NEXT: #define __STDC_UTF_32__ 1
 // AARCH64_C: #define __STDC_VERSION__ 201710L
 // AARCH64-NEXT: #define __STDC__ 1
+// AARCH64-NEXT: #define __UINT16_C(c) c
 // AARCH64-NEXT: #define __UINT16_C_SUFFIX__
 // AARCH64-NEXT: #define __UINT16_FMTX__ "hX"
 // AARCH64-NEXT: #define __UINT16_FMTo__ "ho"
 // AARCH64-NEXT: #define __UINT16_FMTu__ "hu"
 // AARCH64-NEXT: #define __UINT16_FMTx__ "hx"
 // AARCH64-NEXT: #define __UINT16_MAX__ 65535
 // AARCH64-NEXT: #define __UINT16_TYPE__ unsigned short
+// AARCH64-NEXT: #define __UINT32_C(c) c##U
 // AARCH64-NEXT: #define __UINT32_C_SUFFIX__ U
 // AARCH64-NEXT: #define __UINT32_FMTX__ "X"
 // AARCH64-NEXT: #define __UINT32_FMTo__ "o"
 // AARCH64-NEXT: #define __UINT32_FMTu__ "u"
 // AARCH64-NEXT: #define __UINT32_FMTx__ "x"
 // AARCH64-NEXT: #define __UINT32_MAX__ 4294967295U
 // AARCH64-NEXT: #define __UINT32_TYPE__ unsigned int
+// AARCH64-NEXT: #define __UINT64_C(c) c##UL
 // AARCH64-NEXT: #define __UINT64_C_SUFFIX__ UL
 // AARCH64-NEXT: #define __UINT64_FMTX__ "lX"
 // AARCH64-NEXT: #define __UINT64_FMTo__ "lo"
 // AARCH64-NEXT: #define __UINT64_FMTu__ "lu"
 // AARCH64-NEXT: #define __UINT64_FMTx__ "lx"
 // AARCH64-NEXT: #define __UINT64_MAX__ 18446744073709551615UL
 // AARCH64-NEXT: #define __UINT64_TYPE__ long unsigned int
+// AARCH64-NEXT: #define __UINT8_C(c) c
 // AARCH64-NEXT: #define __UINT8_C_SUFFIX__
 // AARCH64-NEXT: #define __UINT8_FMTX__ "hhX"
 // AARCH64-NEXT: #define __UINT8_FMTo__ "hho"
 // AARCH64-NEXT: #define __UINT8_FMTu__ "hhu"
 // AARCH64-NEXT: #define __UINT8_FMTx__ "hhx"
 // AARCH64-NEXT: #define __UINT8_MAX__ 255
 // AARCH64-NEXT: #define __UINT8_TYPE__ unsigned char
+// AARCH64-NEXT: #define __UINTMAX_C(c) c##UL
 // AARCH64-NEXT: #define __UINTMAX_C_SUFFIX__ UL
 // AARCH64-NEXT: #define __UINTMAX_FMTX__ "lX"
 // AARCH64-NEXT: #define __UINTMAX_FMTo__ "lo"
@@ -435,26 +445,31 @@
 // AARCH64-DARWIN: #define __FLT_MIN__ 1.17549435e-38F
 // AARCH64-DARWIN: #define __FLT_RADIX__ 2
 // AARCH64-DARWIN: #define __FUNCTION_MULTI_VERSIONING_SUPPORT_LEVEL 202430
+// AARCH64-DARWIN: #define __INT16_C(c) c
 // AARCH64-DARWIN: #define __INT16_C_SUFFIX__
 // AARCH64-DARWIN: #define __INT16_FMTd__ "hd"
 // AARCH64-DARWIN: #define __INT16_FMTi__ "hi"
 // AARCH64-DARWIN: #define __INT16_MAX__ 32767
 // AARCH64-DARWIN: #define __INT16_TYPE__ short
+// AARCH64-DARWIN: #define __INT32_C(c) c
 // AARCH64-DARWIN: #define __INT32_C_SUFFIX__
 // AARCH64-DARWIN: #define __INT32_FMTd__ "d"
 // AARCH64-DARWIN: #define __INT32_FMTi__ "i"
 // AARCH64-DARWIN: #define __INT32_MAX__ 2147483647
 // AARCH64-DARWIN: #define __INT32_TYPE__ int
+// AARCH64-DARWIN: #define __INT64_C(c) c##LL
 // AARCH64-DARWIN: #define __INT64_C_SUFFIX__ LL
 // AARCH64-DARWIN: #define __INT64_FMTd__ "lld"
 // AARCH64-DARWIN: #define __INT64_FMTi__ "lli"
 // AARCH64-DARWIN: #define __INT64_MAX__ 9223372036854775807LL
 // AARCH64-DARWIN: #define __INT64_TYPE__ long long int
+// AARCH64-DARWIN: #define __INT8_C(c) c
 // AARCH64-DARWIN: #define __INT8_C_SUFFIX__
 // AARCH64-DARWIN: #define __INT8_FMTd__ "hhd"
 // AARCH64-DARWIN: #define __INT8_FMTi__ "hhi"
 // AARCH64-DARWIN: #define __INT8_MAX__ 127
 // AARCH64-DARWIN: #define __INT8_TYPE__ signed char
+// AARCH64-DARWIN: #define __INTMAX_C(c) c##L
 // AARCH64-DARWIN: #define __INTMAX_C_SUFFIX__ L
 // AARCH64-DARWIN: #define __INTMAX_FMTd__ "ld"
 // AARCH64-DARWIN: #define __INTMAX_FMTi__ "li"
@@ -538,18 +553,23 @@
 // AARCH64-DARWIN: #define __SIZE_MAX__ 18446744073709551615UL
 // AARCH64-DARWIN: #define __SIZE_TYPE__ long unsigned int
 // AARCH64-DARWIN: #define __SIZE_WIDTH__ 64
+// AARCH64-DARWIN: #define __UINT16_C(c) c
 // AARCH64-DARWIN: #define __UINT16_C_SUFFIX__
 // AARCH64-DARWIN: #define __UINT16_MAX__ 65535
 // AARCH64-DARWIN: #define __UINT16_TYPE__ unsigned short
+// AARCH64-DARWIN: #define __UINT32_C(c) c##U
 // AARCH64-DARWIN: #define __UINT32_C_SUFFIX__ U
 // AARCH64-DARWIN: #define __UINT32_MAX__ 4294967295U
 // AARCH64-DARWIN: #define __UINT32_TYPE__ unsigned int
+// AARCH64-DARWIN: #define __UINT64_C(c) c##ULL
 // AARCH64-DARWIN: #define __UINT64_C_SUFFIX__ ULL
 // AARCH64-DARWIN: #define __UINT64_MAX__ 18446744073709551615ULL
 // AARCH64-DARWIN: #define __UINT64_TYPE__ long long unsigned int
+// AARCH64-DARWIN: #define __UINT8_C(c) c
 // AARCH64-DARWIN: #define __UINT8_C_SUFFIX__
 // AARCH64-DARWIN: #define __UINT8_MAX__ 255
 // AARCH64-DARWIN: #define __UINT8_TYPE__ unsigned char
+// AARCH64-DARWIN: #define __UINTMAX_C(c) c##UL
 // AARCH64-DARWIN: #define __UINTMAX_C_SUFFIX__ UL
 // AARCH64-DARWIN: #define __UINTMAX_MAX__ 18446744073709551615UL
 // AARCH64-DARWIN: #define __UINTMAX_TYPE__ long unsigned int
@@ -703,18 +723,23 @@
 // AARCH64-MSVC: #define __STDC_UTF_32__ 1
 // AARCH64-MSVC: #define __STDC_VERSION__ 201710L
 // AARCH64-MSVC: #define __STDC__ 1
+// AARCH64-MSVC: #define __UINT16_C(c) c
 // AARCH64-MSVC: #define __UINT16_C_SUFFIX__
 // AARCH64-MSVC: #define __UINT16_MAX__ 65535
 // AARCH64-MSVC: #define __UINT16_TYPE__ unsigned short
+// AARCH64-MSVC: #define __UINT32_C(c) c##U
 // AARCH64-MSVC: #define __UINT32_C_SUFFIX__ U
 // AARCH64-MSVC: #define __UINT32_MAX__ 4294967295U
 // AARCH64-MSVC: #define __UINT32_TYPE__ unsigned int
+// AARCH64-MSVC: #define __UINT64_C(c) c##ULL
 // AARCH64-MSVC: #define __UINT64_C_SUFFIX__ ULL
 // AARCH64-MSVC: #define __UINT64_MAX__ 18446744073709551615ULL
 // AARCH64-MSVC: #define __UINT64_TYPE__ long long unsigned int
+// AARCH64-MSVC: #define __UINT8_C(c) c
 // AARCH64-MSVC: #define __UINT8_C_SUFFIX__
 // AARCH64-MSVC: #define __UINT8_MAX__ 255
 // AARCH64-MSVC: #define __UINT8_TYPE__ unsigned char
+// AARCH64-MSVC: #define __UINTMAX_C(c) c##ULL
 // AARCH64-MSVC: #define __UINTMAX_C_SUFFIX__ ULL
 // AARCH64-MSVC: #define __UINTMAX_MAX__ 18446744073709551615ULL
 // AARCH64-MSVC: #define __UINTMAX_TYPE__ long long unsigned int
@@ -867,26 +892,31 @@
 // ARM64EC-MSVC: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
 // ARM64EC-MSVC: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
 // ARM64EC-MSVC: #define __HAVE_FUNCTION_MULTI_VERSIONING 1
+// ARM64EC-MSVC: #define __INT16_C(c) c
 // ARM64EC-MSVC: #define __INT16_C_SUFFIX__
 // ARM64EC-MSVC: #define __INT16_FMTd__ "hd"
 // ARM64EC-MSVC: #define __INT16_FMTi__ "hi"
 // ARM64EC-MSVC: #define __INT16_MAX__ 32767
 // ARM64EC-MSVC: #define __INT16_TYPE__ short
+// ARM64EC-MSVC: #define __INT32_C(c) c
 // ARM64EC-MSVC: #define __INT32_C_SUFFIX__
 // ARM64EC-MSVC: #define __INT32_FMTd__ "d"
 // ARM64EC-MSVC: #define __INT32_FMTi__ "i"
 // ARM64EC-MSVC: #define __INT32_MAX__ 2147483647
 // ARM64EC-MSVC: #define __INT32_TYPE__ int
+// ARM64EC-MSVC: #define __INT64_C(c) c##LL
 // ARM64EC-MSVC: #define __INT64_C_SUFFIX__ LL
 // ARM64EC-MSVC: #define __INT64_FMTd__ "lld"
 // ARM64EC-MSVC: #define __INT64_FMTi__ "lli"
 // ARM64EC-MSVC: #define __INT64_MAX__ 9223372036854775807LL
 // ARM64EC-MSVC: #define __INT64_TYPE__ long long int
+// ARM64EC-MSVC: #define __INT8_C(c) c
 // ARM64EC-MSVC: #define __INT8_C_SUFFIX__
 // ARM64EC-MSVC: #define __INT8_FMTd__ "hhd"
 // ARM64EC-MSVC: #define __INT8_FMTi__ "hhi"
 // ARM64EC-MSVC: #define __INT8_MAX__ 127
 // ARM64EC-MSVC: #define __INT8_TYPE__ signed char
+// ARM64EC-MSVC: #define __INTMAX_C(c) c##LL
 // ARM64EC-MSVC: #define __INTMAX_C_SUFFIX__ LL
 // ARM64EC-MSVC: #define __INTMAX_FMTd__ "lld"
 // ARM64EC-MSVC: #define __INTMAX_FMTi__ "lli"
@@ -1013,34 +1043,39 @@
 // ARM64EC-MSVC: #define __STDC_UTF_32__ 1
 // ARM64EC-MSVC: #define __STDC_VERSION__ 201710L
 // ARM64EC-MSVC: #define __STDC__ 1
+// ARM64EC-MSVC: #define __UINT16_C(c) c
 // ARM64EC-MSVC: #define __UINT16_C_SUFFIX__
 // ARM64EC-MSVC: #define __UINT16_FMTX__ "hX"
 // ARM64EC-MSVC: #define __UINT16_FMTo__ "ho"
 // ARM64EC-MSVC: #define __UINT16_FMTu__ "hu"
 // ARM64EC-MSVC: #define __UINT16_FMTx__ "hx"
 // ARM64EC-MSVC: #define __UINT16_MAX__ 65535
 // ARM64EC-MSVC: #define __UINT16_TYPE__ unsigned short
+// ARM64EC-MSVC: #define __UINT32_C(c) c##U
 // ARM64EC-MSVC: #define __UINT32_C_SUFFIX__ U
 // ARM64EC-MSVC: #define __UINT32_FMTX__ "X"
 // ARM64EC-MSVC: #define __UINT32_FMTo__ "o"
 // ARM64EC-MSVC: #define __UINT32_FMTu__ "u"
 // ARM64EC-MSVC: #define __UINT32_FMTx__ "x"
 // ARM64EC-MSVC: #define __UINT32_MAX__ 4294967295U
 // ARM64EC-MSVC: #define __UINT32_TYPE__ unsigned int
+// ARM64EC-MSVC: #define __UINT64_C(c) c##ULL
 // ARM64EC-MSVC: #define __UINT64_C_SUFFIX__ ULL
 // ARM64EC-MSVC: #define __UINT64_FMTX__ "llX"
 // ARM64EC-MSVC: #define __UINT64_FMTo__ "llo"
 // ARM64EC-MSVC: #define __UINT64_FMTu__ "llu"
 // ARM64EC-MSVC: #define __UINT64_FMTx__ "llx"
 // ARM64EC-MSVC: #define __UINT64_MAX__ 18446744073709551615ULL
 // ARM64EC-MSVC: #define __UINT64_TYPE__ long long unsigned int
+// ARM64EC-MSVC: #define __UINT8_C(c) c
 // ARM64EC-MSVC: #define __UINT8_C_SUFFIX__
 // ARM64EC-MSVC: #define __UINT8_FMTX__ "hhX"
 // ARM64EC-MSVC: #define __UINT8_FMTo__ "hho"
 // ARM64EC-MSVC: #define __UINT8_FMTu__ "hhu"
 // ARM64EC-MSVC: #define __UINT8_FMTx__ "hhx"
 // ARM64EC-MSVC: #define __UINT8_MAX__ 255
 // ARM64EC-MSVC: #define __UINT8_TYPE__ unsigned char
+// ARM64EC-MSVC: #define __UINTMAX_C(c) c##ULL
 // ARM64EC-MSVC: #define __UINTMAX_C_SUFFIX__ ULL
 // ARM64EC-MSVC: #define __UINTMAX_FMTX__ "llX"
 // ARM64EC-MSVC: #define __UINTMAX_FMTo__ "llo"