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ed0cdf0e05
On ELF-based platforms (and maybe others?) it's possible for a shared library, when dynamically loaded into the backend, to call the backend versions of src/port and src/common functions rather than the frontend versions that are actually linked into the shlib. This is definitely not what we want, because the frontend versions often behave slightly differently. Up to now it's been "slight" enough that nobody noticed; but with the addition of SCRAM support functions in src/common, we're observing crashes due to the difference between palloc and malloc memory allocation rules, as reported in bug #15367 from Jeremy Evans. The purpose of this patch is to create a direct test for this type of mis-linking, so that we know whether any given platform requires extra measures to prevent using the wrong functions. If the test fails, it will lead to connection failures in the contrib/postgres_fdw regression test. At the moment, *BSD platforms using ELF format are known to have the problem and can be expected to fail; but we need to know whether anything else does, and we need a reliable ongoing check for future platforms. Actually fixing the problem will be the subject of later commit(s). Discussion: https://postgr.es/m/153626613985.23143.4743626885618266803@wrigleys.postgresql.org
37 lines
1.2 KiB
C
37 lines
1.2 KiB
C
/*-------------------------------------------------------------------------
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* link-canary.c
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* Detect whether src/common functions came from frontend or backend.
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*
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* Copyright (c) 2018, PostgreSQL Global Development Group
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*
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* IDENTIFICATION
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* src/common/link-canary.c
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*
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*-------------------------------------------------------------------------
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*/
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#include "c.h"
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#include "common/link-canary.h"
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/*
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* This function just reports whether this file was compiled for frontend
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* or backend environment. We need this because in some systems, mainly
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* ELF-based platforms, it is possible for a shlib (such as libpq) loaded
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* into the backend to call a backend function named XYZ in preference to
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* the shlib's own function XYZ. That's bad if the two functions don't
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* act identically. This exact situation comes up for many functions in
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* src/common and src/port, where the same function names exist in both
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* libpq and the backend but they don't act quite identically. To verify
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* that appropriate measures have been taken to prevent incorrect symbol
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* resolution, libpq should test that this function returns true.
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*/
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bool
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pg_link_canary_is_frontend(void)
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{
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#ifdef FRONTEND
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return true;
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#else
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return false;
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#endif
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}
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