/usr/share/aclocal/ax_dll_string.m4 is in autoconf-archive 20170928-2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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# https://www.gnu.org/software/autoconf-archive/ax_dll_string.html
# ===========================================================================
#
# SYNOPSIS
#
# AX_DLL_STRING
#
# DESCRIPTION
#
# Tests for a bug currently in g++ 3.4.4 on Cygwin (maybe other targets
# with statically linked libstdc++?) where passing an empty std::string to
# a dll will cause a crash on destruction due to incorrect memory
# handling. See bug 24196 in gcc's bugzilla for more details:
# http://gcc.gnu.org/bugzilla/show_bug.cgi?id=24196
#
# LICENSE
#
# Copyright (c) 2008 Steven Brown <swbrown@variadic.org>
#
# Copying and distribution of this file, with or without modification, are
# permitted in any medium without royalty provided the copyright notice
# and this notice are preserved. This file is offered as-is, without any
# warranty.
#serial 8
dnl Plan: compile conftest-dll.cc, conftest-exe.cc. It has a 'crash' param
dnl that can be passed. Verify the compile worked and we can run it normally
dnl ok. Then, pass 'crash', test if it crashed, fail.
AC_DEFUN([AX_DLL_STRING],
[
AC_MSG_CHECKING(if the dll string test can be compiled)
cat << EOF > conftest-dll.cc
[
#include <string>
using namespace std;
void testit(std::string (*contentGet)()) {
contentGet();
}
]
EOF
cat << EOF > conftest-exe.cc
[
#include <string>
#include <cstring>
using namespace std;
extern void testit(std::string (*contentGet)());
std::string contentGet() {
return string(""); // Anything other than empty string works.
}
int main(int argc, char *argv[]) {
if(argc == 2 && strcmp(argv[1], "crash") == 0) {
testit(&contentGet);
}
return 0;
}
]
EOF
$CXX -shared $CFLAGS $CPPFLAGS conftest-dll.cc -o conftest-dll.dll >&AS_MESSAGE_LOG_FD && $CXX $CFLAGS $CPPFLAGS conftest-exe.cc conftest-dll.dll -o conftest-exe.exe >& AS_MESSAGE_LOG_FD
if test x"$?" = x"0"; then
AC_MSG_RESULT(yes)
dnl Make sure it runs normally first.
AC_MSG_CHECKING(if the dll string test is usable)
if /bin/sh -c "(LD_LIBRARY_PATH=\"$PWD\" ./conftest-exe.exe)" >& AS_MESSAGE_LOG_FD 2>&1; then
AC_MSG_RESULT(yes)
dnl Now we can check for the bug.
AC_MSG_CHECKING(if the dll string test is affected by gcc bug 24196)
if ! /bin/sh -c "(LD_LIBRARY_PATH=\"$PWD\" ./conftest-exe.exe crash)" >& AS_MESSAGE_LOG_FD 2>&1; then
AC_MSG_RESULT(yes)
dnl We have the bug, user'll need to fix it.
AC_MSG_ERROR([*** This toolchain is affected by gcc bug 24196. For Cygwin as of 4/8/2006, you can downgrade to gcc/g++ 3.3.3 or check if there is a newer compiler available that's fixed.])
else
AC_MSG_RESULT(no)
fi
else
AC_MSG_RESULT(no)
fi
else
AC_MSG_RESULT(no)
fi
])
|