build-aux/link-warning.h

   1 /* GL_LINK_WARNING("literal string") arranges to emit the literal string as
   2    a linker warning on most glibc systems.
   3    We use a linker warning rather than a preprocessor warning, because
   4    #warning cannot be used inside macros.  */
   5 #ifndef GL_LINK_WARNING
   6   /* This works on platforms with GNU ld and ELF object format.
   7      Testing __GLIBC__ is sufficient for asserting that GNU ld is in use.
   8      Testing __ELF__ guarantees the ELF object format.
   9      Testing __GNUC__ is necessary for the compound expression syntax.  */
  10 # if defined __GLIBC__ && defined __ELF__ && defined __GNUC__
  11 #  define GL_LINK_WARNING(message) \
  12      GL_LINK_WARNING1 (__FILE__, __LINE__, message)
  13 #  define GL_LINK_WARNING1(file, line, message) \
  14      GL_LINK_WARNING2 (file, line, message)  /* macroexpand file and line */
  15 #  define GL_LINK_WARNING2(file, line, message) \
  16      GL_LINK_WARNING3 (file ":" #line ": warning: " message)
  17 #  define GL_LINK_WARNING3(message) \
  18      ({ static const char warning[sizeof (message)]             \
  19           __attribute__ ((__unused__,                           \
  20                           __section__ (".gnu.warning"),         \
  21                           __aligned__ (1)))                     \
  22           = message "\n";                                       \
  23         (void)0;                                                \
  24      })
  25 # else
  26 #  define GL_LINK_WARNING(message) ((void) 0)
  27 # endif
  28 #endif