[clang] [Clang] Add predefined macros for integer constants to implement section 7.18.4 of ISO/IEC 9899:1999 in `<stdint.h>` in a safe way (PR #123514)
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Sun Jan 19 06:46:36 PST 2025
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Manuel Sainz de Baranda y Goñi (redcode)
<details>
<summary>Changes</summary>
This small PR makes Clang predefine the following macros:
```
__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;
}
```
---
Full diff: https://github.com/llvm/llvm-project/pull/123514.diff
1 Files Affected:
- (modified) clang/lib/Frontend/InitPreprocessor.cpp (+10-4)
``````````diff
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 29723b573e771a..17f624e9645395 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/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);
``````````
</details>
https://github.com/llvm/llvm-project/pull/123514
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