Re: Issue with dllexport/dllimport inline function

[xclaesse@gmail.com]

Le mardi 11 octobre 2022 à 21:35 +0800, LIU Hao a écrit :
> 在 2022/10/11 21:28, LIU Hao via Gcc 写道:
> > 
> > Did you have any declarations that had no `__gnu_inline__`? GNU
> > inline functions are supposed to be 
> > emitted out of line, even when its address is taken.
> > 
> 
> This should be 'to be never emitted out of line'. Sorry for that.

I have one .c file, part of libglib-2.0-0.dll, that has that line:

```
extern int g_strcmp0 (const char *str1, const char *str2);
```

The header file has that:
```
GLIB_INLINE
int     g_strcmp0                       (const char     *str1,
                                         const char     *str2)
{
  if (!str1)
    return -(str1 != str2);
  if (!str2)
    return str1 != str2;
  return strcmp (str1, str2);
}
```

I now define GLIB_INLINE that way:
```
#if (defined(_WIN32) || defined(__CYGWIN__)) &&
!defined(GLIB_STATIC_COMPILATION)
#  define _GLIB_EXPORT __declspec(dllexport)
#  define _GLIB_IMPORT __declspec(dllimport)
#elif __GNUC__ >= 4
#  define _GLIB_EXPORT __attribute__((visibility("default")))
#  define _GLIB_IMPORT
#else
#  define _GLIB_EXPORT
#  define _GLIB_IMPORT
#endif
#ifdef GLIB_COMPILATION
#  define _GLIB_API _GLIB_EXPORT
#  define GLIB_INLINE __attribute__((__dllexport__))
__attribute__((__gnu_inline__)) extern inline
#else
#  define _GLIB_API _GLIB_IMPORT
#  if defined(__has_attribute) && __has_attribute(__gnu_inline__)
     // https://gcc.gnu.org/pipermail/gcc/2022-October/239592.html
#    define GLIB_INLINE __attribute__((__gnu_inline__)) extern inline
#  else
#    define GLIB_INLINE _GLIB_EXPORT extern inline
#  endif
#endif
```

`GLIB_COMPILATION` is defined when compiling libglib-2.0-0.dll but not
when compiling other dlls or applications.

The linker issue actually happens when linking libglib-2.0-0.dll,
multiple definition happens for all .c files that actually uses
g_strcmp0:
```
/usr/bin/x86_64-w64-mingw32-ld: glib/libglib-2.0-
0.dll.p/deprecated_grel.c.obj: in function `g_strcmp0':
/home/xclaesse/programmation/glib/builddir/../glib/gtestutils.h:245:
multiple definition of `g_strcmp0'; glib/libglib-2.0-
0.dll.p/deprecated_gcache.c.obj:/home/xclaesse/programmation/glib/build
dir/../glib/gtestutils.h:245: first defined here
```