[libc-commits] [PATCH] D154036: [libc] Add support for creating wrapper headers for offloading in clang

[Joseph Huber via Phabricator via libc-commits]

jhuber6 added a comment.

For reference, here is what one of the newly generated headers looks like that is used.

  #ifndef __LLVM_LIBC_DECLARATIONS_STDIO_H
  #define __LLVM_LIBC_DECLARATIONS_STDIO_H
  
  #ifndef __LIBC_ATTRS
  #define __LIBC_ATTRS
  #endif
  
  #ifdef __cplusplus
  extern "C" {
  #endif
  
  int puts(const char *__restrict) __LIBC_ATTRS;
  
  int fputs(const char *__restrict, FILE *__restrict) __LIBC_ATTRS;
  
  extern FILE * stdin __LIBC_ATTRS;
  extern FILE * stdout __LIBC_ATTRS;
  extern FILE * stderr __LIBC_ATTRS;
  
  #ifdef __cplusplus
  }
  #endif

Unfortunately I have already run into a few problems with the re-declarations given the GNU `libc` headers. Here is the error message when including `string.h` now,

  /home/jhuber/Documents/llvm/clang/lib/clang/17/include/llvm_libc_wrappers/llvm-libc-decls/string.h:54:8: error: 'strstr' is missing exception specification 'noexcept(true)'
     54 | char * strstr(const char *, const char *) __LIBC_ATTRS;
        |        ^
  /usr/include/string.h:343:1: note: previous declaration is here
    343 | strstr (const char *__haystack, const char *__needle) __THROW
        | ^
  5 errors generated.

This occurs for `memchr`, `strchr`, `strpbrk`, `strchr`, and `strstr`. If you define `__LIBC_ATTRS` to the `noexcept(true)` you get a different error,

  /home/jhuber/Documents/llvm/clang/lib/clang/17/include/llvm_libc_wrappers/llvm-libc-decls/string.h:54:8: error: functions that differ only in their return type cannot be overloaded
     54 | char * strstr(const char *, const char *) __LIBC_ATTRS;
        | ~~~~~~ ^
  /usr/include/string.h:343:1: note: previous definition is here
    343 | __extern_always_inline const char *
        |                              ~~~~~~
    344 | strstr (const char *__haystack, const char *__needle) __THROW
        | ^

Looking at the definitions, they look like this in the GNU headers,

  extern char *strstr (char *__haystack, const char *__needle)    
       __THROW __asm ("strstr") __attribute_pure__ __nonnull ((1, 2));    
  extern const char *strstr (const char *__haystack, const char *__needle)    
       __THROW __asm ("strstr") __attribute_pure__ __nonnull ((1, 2));

Does anyone have any suggestions on working around this? The other supported headers work as far as I can tell.


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D154036/new/

https://reviews.llvm.org/D154036