src/common/link-canary.c

   1 /*-------------------------------------------------------------------------
   2  * link-canary.c
   3  *        Detect whether src/common functions came from frontend or backend.
   4  *
   5  * Copyright (c) 2018-2021, PostgreSQL Global Development Group
   6  *
   7  * IDENTIFICATION
   8  *        src/common/link-canary.c
   9  *
  10  *-------------------------------------------------------------------------
  11  */
  12 #include "c.h"
  13
  14 #include "common/link-canary.h"
  15
  16 /*
  17  * This function just reports whether this file was compiled for frontend
  18  * or backend environment.  We need this because in some systems, mainly
  19  * ELF-based platforms, it is possible for a shlib (such as libpq) loaded
  20  * into the backend to call a backend function named XYZ in preference to
  21  * the shlib's own function XYZ.  That's bad if the two functions don't
  22  * act identically.  This exact situation comes up for many functions in
  23  * src/common and src/port, where the same function names exist in both
  24  * libpq and the backend but they don't act quite identically.  To verify
  25  * that appropriate measures have been taken to prevent incorrect symbol
  26  * resolution, libpq should test that this function returns true.
  27  */
  28 bool
  29 pg_link_canary_is_frontend(void)
  30 {
  31 #ifdef FRONTEND
  32         return true;
  33 #else
  34         return false;
  35 #endif
  36 }