link_warning.c

// When a reference to SYMBOL is encountered, the linker will emit a warning
// message MSG. We want the .gnu.warning.SYMBOL section to be unallocated. See
// https://sourceware.org/git?p=glibc.git;a=blob;f=include/libc-symbols.h
#if defined(__ELF__) && defined(__GNUC__)
#define __sec_comment "\n\t#"
#define link_warning(symbol, msg)                                              \
  __asm__(".section .gnu.warning." #symbol "\n\t.previous");                   \
  static const char __evoke_link_warning_##symbol[]                            \
      __attribute__((used, section(".gnu.warning." #symbol __sec_comment))) =  \
          msg;
#else
#define link_warning(symbol, msg)
#endif