From 43a7099781d13b1ccd119acf955b8dce6fa0c279 Mon Sep 17 00:00:00 2001
From: Michael Paquier <michael@paquier.xyz>
Date: Thu, 4 Dec 2025 09:12:58 +0900
Subject: [PATCH v5 1/2] libpq: centralize exit() check logic and unify
 Makefile/Meson behavior

Move the libpq exit() reference check into a shared Perl script
(libpq-exit-check) and use it for both autoconf/Makefile and Meson
builds.  This avoids duplicated logic and ensures consistent
platform-specific handling of whitelisted symbols.

The script now receives the full path to `nm`, detected at the
top-level configure using AC_PATH_PROG and propagated via NM_PROG.
Both Makefile and Meson invoke the script with --nm=<path>.

Platform-specific behavior (Solaris skip, Windows skip, whitelisted
symbols, nm availability checks) is centralized inside the script.

This makes the two build systems apply the same exit() policy and keeps
all rules in one place.
---
 src/interfaces/libpq/Makefile       | 21 ++-----
 src/interfaces/libpq/libpq-check.pl | 86 +++++++++++++++++++++++++++++
 src/interfaces/libpq/meson.build    | 19 +++++++
 configure                           | 42 ++++++++++++++
 configure.ac                        |  2 +
 meson.build                         |  1 +
 src/Makefile.global.in              |  1 +
 7 files changed, 155 insertions(+), 17 deletions(-)
 create mode 100755 src/interfaces/libpq/libpq-check.pl

diff --git a/src/interfaces/libpq/Makefile b/src/interfaces/libpq/Makefile
index da6650066d46..1b7d3ecf8aac 100644
--- a/src/interfaces/libpq/Makefile
+++ b/src/interfaces/libpq/Makefile
@@ -129,25 +129,12 @@ $(shlib): $(OBJS_SHLIB)
 $(stlib): override OBJS += $(OBJS_STATIC)
 $(stlib): $(OBJS_STATIC)
 
-# Check for functions that libpq must not call, currently just exit().
-# (Ideally we'd reject abort() too, but there are various scenarios where
-# build toolchains insert abort() calls, e.g. to implement assert().)
-# If nm doesn't exist or doesn't work on shlibs, this test will do nothing,
-# which is fine.  The exclusion of __cxa_atexit is necessary on OpenBSD,
-# which seems to insert references to that even in pure C code. Excluding
-# __tsan_func_exit is necessary when using ThreadSanitizer data race detector
-# which use this function for instrumentation of function exit.
-# Skip the test when profiling, as gcc may insert exit() calls for that.
-# Also skip the test on platforms where libpq infrastructure may be provided
-# by statically-linked libraries, as we can't expect them to honor this
-# coding rule.
+# Check for functions that libpq must not call.  See libpq-check.pl for the
+# full set of platform rules.  Skip the test when profiling, as gcc may
+# insert exit() calls for that.
 libpq-refs-stamp: $(shlib)
 ifneq ($(enable_coverage), yes)
-ifeq (,$(filter solaris,$(PORTNAME)))
-	@if nm -A -u $< 2>/dev/null | grep -v -e __cxa_atexit -e __tsan_func_exit | grep exit; then \
-		echo 'libpq must not be calling any function which invokes exit'; exit 1; \
-	fi
-endif
+	$(PERL) libpq-check.pl --input_file $< --nm='$(NM)'
 endif
 	touch $@
 
diff --git a/src/interfaces/libpq/libpq-check.pl b/src/interfaces/libpq/libpq-check.pl
new file mode 100755
index 000000000000..274e873d1fca
--- /dev/null
+++ b/src/interfaces/libpq/libpq-check.pl
@@ -0,0 +1,86 @@
+#!/usr/bin/perl
+#
+# src/interfaces/libpq/libpq-check.pl
+#
+# Copyright (c) 2025, PostgreSQL Global Development Group
+#
+# Check that the state of a libpq library.  Currently, this script checks
+# that exit() is not called, because client libraries must not terminate
+# the host application.
+#
+# This script is called by both Makefile and Meson.
+
+use strict;
+use warnings FATAL => 'all';
+
+use Getopt::Long;
+use Config;
+
+my $nm_path;
+my $input_file;
+my $stamp_file;
+my @problematic_lines;
+
+Getopt::Long::GetOptions(
+	'nm:s' => \$nm_path,
+	'input_file:s' => \$input_file,
+	'stamp_file:s' => \$stamp_file) or die "$0: wrong arguments\n";
+
+die "$0: --input_file must be specified\n" unless defined $input_file;
+die "$0: --nm must be specified\n" unless defined $nm_path and -x $nm_path;
+
+sub create_stamp_file
+{
+	if (!(-f $stamp_file))
+	{
+		open my $fh, '>', $stamp_file
+		  or die "can't open $stamp_file: $!";
+		close $fh;
+	}
+}
+
+# ---- Skip on Windows and Solaris ----
+if (   $Config{osname} =~ /MSWin32|cygwin|msys/i
+	|| $Config{osname} =~ /solaris/i)
+{
+	exit 0;
+}
+
+# Run nm to scan for symbols.  If nm fails at runtime, skip the check.
+open my $fh, '-|', "$nm_path -A -u $input_file 2>/dev/null"
+  or exit 0;
+
+while (<$fh>)
+{
+	# Set of symbols allowed:
+	#     __cxa_atexit     - injected by some libcs (e.g., OpenBSD)
+	#     __tsan_func_exit - ThreadSanitizer instrumentation
+
+	next if /__cxa_atexit/;
+	next if /__tsan_func_exit/;
+
+	# Anything containing "exit" is suspicious.
+	# (Ideally we should reject abort() too, but there are various scenarios
+	# where build toolchains insert abort() calls, e.g. to implement assert().)
+	if (/exit/)
+	{
+		push @problematic_lines, $_;
+	}
+}
+close $fh;
+
+if (@problematic_lines)
+{
+	print "libpq must not be calling any function which invokes exit\n";
+	print "Problematic symbol references:\n";
+	print @problematic_lines;
+
+	exit 1;
+}
+# Create stamp file, if required
+if (defined($stamp_file))
+{
+	create_stamp_file();
+}
+
+exit 0;
diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build
index a74e885b169d..e71ee9058030 100644
--- a/src/interfaces/libpq/meson.build
+++ b/src/interfaces/libpq/meson.build
@@ -85,6 +85,25 @@ libpq = declare_dependency(
   include_directories: [include_directories('.')]
 )
 
+# Check for functions that libpq must not call.  See libpq-check.pl for the
+# full set of platform rules.  Skip the test when profiling, as gcc may
+# insert exit() calls for that.
+if nm.found() and not get_option('b_coverage')
+  custom_target(
+    'libpq-check',
+    input: libpq_so,
+    output: 'libpq-refs-stamp',
+    command: [
+      perl,
+        files('libpq-check.pl'),
+          '--input_file', '@INPUT@',
+          '--stamp_file', '@OUTPUT@',
+	  '--nm', nm.full_path()
+    ],
+    build_by_default: true,
+  )
+endif
+
 private_deps = [
   frontend_stlib_code,
   libpq_deps,
diff --git a/configure b/configure
index 3a0ed11fa8e2..ec35de5ba657 100755
--- a/configure
+++ b/configure
@@ -682,6 +682,7 @@ FLEXFLAGS
 FLEX
 BISONFLAGS
 BISON
+NM
 MKDIR_P
 LN_S
 TAR
@@ -10162,6 +10163,47 @@ case $MKDIR_P in
   *install-sh*) MKDIR_P='\${SHELL} \${top_srcdir}/config/install-sh -c -d';;
 esac
 
+# Extract the first word of "nm", so it can be a program name with args.
+set dummy nm; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_NM+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $NM in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_NM="$NM" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_NM="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+NM=$ac_cv_path_NM
+if test -n "$NM"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $NM" >&5
+$as_echo "$NM" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+
 if test -z "$BISON"; then
   for ac_prog in bison
 do
diff --git a/configure.ac b/configure.ac
index c2413720a188..7284f1ff6229 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1214,6 +1214,8 @@ case $MKDIR_P in
   *install-sh*) MKDIR_P='\${SHELL} \${top_srcdir}/config/install-sh -c -d';;
 esac
 
+AC_PATH_PROG(NM, nm)
+AC_SUBST(NM)
 PGAC_PATH_BISON
 PGAC_PATH_FLEX
 
diff --git a/meson.build b/meson.build
index 6e7ddd74683c..622598546ae8 100644
--- a/meson.build
+++ b/meson.build
@@ -350,6 +350,7 @@ missing = find_program('config/missing', native: true)
 cp = find_program('cp', required: false, native: true)
 xmllint_bin = find_program(get_option('XMLLINT'), native: true, required: false)
 xsltproc_bin = find_program(get_option('XSLTPROC'), native: true, required: false)
+nm = find_program('nm', required: false, native: true)
 
 bison_flags = []
 if bison.found()
diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index 0aa389bc7101..371cd7eba2c1 100644
--- a/src/Makefile.global.in
+++ b/src/Makefile.global.in
@@ -292,6 +292,7 @@ FLEX = @FLEX@
 FLEXFLAGS = @FLEXFLAGS@ $(LFLAGS)
 DTRACE = @DTRACE@
 DTRACEFLAGS = @DTRACEFLAGS@
+NM = @NM@
 ZIC = @ZIC@
 
 # Linking
-- 
2.51.0