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a3b709cf73
In the name of ABI stability (that is, to avoid a library major version bump for libpq), libpq still exports a version of pqsignal() that we no longer want to use ourselves. However, since that has the same link name as the function exported by src/port/pqsignal.c, there is a link ordering dependency determining which version will actually get used by code that uses libpq as well as libpgport.a. It now emerges that the wrong version has been used by pgbench and psql since commit06843df4arearranged their link commands. This can result in odd failures in pgbench with the -T switch, since its SIGALRM handler will now not be marked SA_RESTART. psql may have some edge-case problems in \watch, too. Since we don't want to depend on link ordering effects anymore, let's fix this in the same spirit asb6c7cfac8: use macros to change the actual link names of the competing functions. We cannot change legacy-pqsignal.c's exported name of course, so the victim has to be src/port/pqsignal.c. In master, rename its exported name to be pqsignal_fe in frontend or pqsignal_be in backend. (We could perhaps have gotten away with using the same symbol in both cases, but since the FE and BE versions now work a little differently, it seems advisable to use different names.) In back branches, rename to pqsignal_fe in frontend but keep it as pqsignal in backend. The frontend change could affect third-party code that is calling pqsignal from libpgport.a or libpgport_shlib.a, but only if the code is compiled against port.h from a different minor release than libpgport. Since we don't support using libpgport as a shared library, it seems unlikely that there will be such a problem. I left the backend symbol unchanged to avoid an ABI break for extensions. This means that the link ordering hazard still exists for any extension that links against libpq. However, none of our own extensions use both pqsignal() and libpq, and we're not making things any worse for third-party extensions that do. Report from Andy Fan, diagnosis by Fujii Masao, patch by me. Back-patch to all supported branches, as06843df4awas. Discussion: https://postgr.es/m/87msfz5qv2.fsf@163.com
66 lines
1.9 KiB
C
66 lines
1.9 KiB
C
/*-------------------------------------------------------------------------
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*
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* pqsignal.c
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* reliable BSD-style signal(2) routine stolen from RWW who stole it
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* from Stevens...
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*
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* Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
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* Portions Copyright (c) 1994, Regents of the University of California
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*
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*
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* IDENTIFICATION
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* src/port/pqsignal.c
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*
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* We now assume that all Unix-oid systems have POSIX sigaction(2)
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* with support for restartable signals (SA_RESTART). We used to also
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* support BSD-style signal(2), but there really shouldn't be anything
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* out there anymore that doesn't have the POSIX API.
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*
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* Windows, of course, is resolutely in a class by itself. In the backend,
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* we don't use this file at all; src/backend/port/win32/signal.c provides
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* pqsignal() for the backend environment. Frontend programs can use
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* this version of pqsignal() if they wish, but beware that this does
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* not provide restartable signals on Windows.
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*
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* ------------------------------------------------------------------------
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*/
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#include "c.h"
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#include <signal.h>
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#if !defined(WIN32) || defined(FRONTEND)
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/*
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* Set up a signal handler, with SA_RESTART, for signal "signo"
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*
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* Returns the previous handler.
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*
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* Note: the actual name of this function is either pqsignal_fe when
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* compiled with -DFRONTEND, or pqsignal when compiled without that.
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* This is to avoid a name collision with libpq's legacy-pqsignal.c.
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*/
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pqsigfunc
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pqsignal(int signo, pqsigfunc func)
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{
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#ifndef WIN32
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struct sigaction act,
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oact;
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act.sa_handler = func;
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sigemptyset(&act.sa_mask);
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act.sa_flags = SA_RESTART;
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#ifdef SA_NOCLDSTOP
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if (signo == SIGCHLD)
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act.sa_flags |= SA_NOCLDSTOP;
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#endif
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if (sigaction(signo, &act, &oact) < 0)
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return SIG_ERR;
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return oact.sa_handler;
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#else /* WIN32 */
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return signal(signo, func);
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#endif
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}
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#endif /* !defined(WIN32) || defined(FRONTEND) */
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