build-aux/link-warning.h

   1 /* A C macro for emitting link time warnings.
   2    Copyright (C) 1995, 1997, 2000, 2002-2003, 2007, 2009-2010 Free Software
   3    Foundation, Inc.
   4
   5    This program is free software: you can redistribute it and/or modify it
   6    under the terms of the GNU Lesser General Public License as published
   7    by the Free Software Foundation; either version 2 of the License, or
   8    (at your option) any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 /* GL_LINK_WARNING("literal string") arranges to emit the literal string as
  19    a linker warning on most glibc systems.
  20    We use a linker warning rather than a preprocessor warning, because
  21    #warning cannot be used inside macros.  */
  22 #ifndef GL_LINK_WARNING
  23   /* This works on platforms with GNU ld and ELF object format.
  24      Testing __GLIBC__ is sufficient for asserting that GNU ld is in use.
  25      Testing __ELF__ guarantees the ELF object format.
  26      Testing __GNUC__ is necessary for the compound expression syntax.  */
  27 # if defined __GLIBC__ && defined __ELF__ && defined __GNUC__
  28 #  define GL_LINK_WARNING(message) \
  29      GL_LINK_WARNING1 (__FILE__, __LINE__, message)
  30 #  define GL_LINK_WARNING1(file, line, message) \
  31      GL_LINK_WARNING2 (file, line, message)  /* macroexpand file and line */
  32 #  define GL_LINK_WARNING2(file, line, message) \
  33      GL_LINK_WARNING3 (file ":" #line ": warning: " message)
  34 #  define GL_LINK_WARNING3(message) \
  35      ({ static const char warning[sizeof (message)]             \
  36           __attribute__ ((__unused__,                           \
  37                           __section__ (".gnu.warning"),         \
  38                           __aligned__ (1)))                     \
  39           = message "\n";                                       \
  40         (void)0;                                                \
  41      })
  42 # else
  43 #  define GL_LINK_WARNING(message) ((void) 0)
  44 # endif
  45 #endif