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From: Jonathan Wakely <redi@gcc.gnu.org> To: gcc-cvs@gcc.gnu.org, libstdc++-cvs@gcc.gnu.org Subject: [gcc r12-8125] libstdc++: Prefer to use mmap instead of malloc in libbacktrace Date: Tue, 12 Apr 2022 21:39:42 +0000 (GMT) [thread overview] Message-ID: <20220412213942.E10F43858C56@sourceware.org> (raw) https://gcc.gnu.org/g:3c742621ed28540cf42d4cfbc2bf03433cd26738 commit r12-8125-g3c742621ed28540cf42d4cfbc2bf03433cd26738 Author: Jonathan Wakely <jwakely@redhat.com> Date: Tue Apr 12 17:56:45 2022 +0100 libstdc++: Prefer to use mmap instead of malloc in libbacktrace As reported in PR libbacktrace/105240, libbacktrace leaks memory when using malloc for allocations. I originally thought it would be simpler to just use malloc unconditionally (because it's supported on all targets) but the leaks make that problematic. This adds libbacktrace's detection for mmap to the libstdc++ configury, so that we use mmap.c and mmapio.c when possible. This avoids the leaks seen previously, at least on linux. libstdc++-v3/ChangeLog: * acinclude.m4 (GLIBCXX_ENABLE_BACKTRACE): Check for mmap. * config.h.in: Regenerate. * configure: Regenerate. Diff: --- libstdc++-v3/acinclude.m4 | 35 +++++++++++++++++++++++----- libstdc++-v3/config.h.in | 3 +++ libstdc++-v3/configure | 59 ++++++++++++++++++++++++++++++++++++++++------- 3 files changed, 83 insertions(+), 14 deletions(-) diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4 index f53461c85a5..eac8aeda48b 100644 --- a/libstdc++-v3/acinclude.m4 +++ b/libstdc++-v3/acinclude.m4 @@ -5003,18 +5003,41 @@ elf64) elfsize=64 ;; esac BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DBACKTRACE_ELF_SIZE=$elfsize" - ALLOC_FILE=alloc.lo - AC_SUBST(ALLOC_FILE) - VIEW_FILE=read.lo - AC_SUBST(VIEW_FILE) - AC_MSG_CHECKING([whether to build libbacktrace support]) if test "$enable_libstdcxx_backtrace" == "auto"; then enable_libstdcxx_backtrace=no fi if test "$enable_libstdcxx_backtrace" == "yes"; then BACKTRACE_SUPPORTED=1 - BACKTRACE_USES_MALLOC=1 + + AC_CHECK_HEADERS(sys/mman.h) + case "${host}" in + *-*-msdosdjgpp) # DJGPP has sys/man.h, but no mmap + have_mmap=no ;; + *-*-*) + have_mmap="$ac_cv_header_sys_mman_h" ;; + esac + + if test "$have_mmap" = "no"; then + VIEW_FILE=read.lo + ALLOC_FILE=alloc.lo + else + VIEW_FILE=mmapio.lo + AC_PREPROC_IFELSE([AC_LANG_SOURCE([ + #include <sys/mman.h> + #if !defined(MAP_ANONYMOUS) && !defined(MAP_ANON) + #error no MAP_ANONYMOUS + #endif + ])], [ALLOC_FILE=mmap.lo], [ALLOC_FILE=alloc.lo]) + fi + AC_SUBST(VIEW_FILE) + AC_SUBST(ALLOC_FILE) + + BACKTRACE_USES_MALLOC=0 + if test "$ALLOC_FILE" = "alloc.lo"; then + BACKTRACE_USES_MALLOC=1 + fi + if test "$ac_has_gthreads" = "yes"; then BACKTRACE_SUPPORTS_THREADS=1 else diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in index f6212de9268..f30a8c51c45 100644 --- a/libstdc++-v3/config.h.in +++ b/libstdc++-v3/config.h.in @@ -420,6 +420,9 @@ /* Define to 1 if you have the <sys/machine.h> header file. */ #undef HAVE_SYS_MACHINE_H +/* Define to 1 if you have the <sys/mman.h> header file. */ +#undef HAVE_SYS_MMAN_H + /* Define to 1 if you have the <sys/param.h> header file. */ #undef HAVE_SYS_PARAM_H diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure index ef80912d0b9..35dc3f49383 100755 --- a/libstdc++-v3/configure +++ b/libstdc++-v3/configure @@ -681,8 +681,8 @@ BACKTRACE_SUPPORTS_THREADS BACKTRACE_USES_MALLOC BACKTRACE_SUPPORTED BACKTRACE_CPPFLAGS -VIEW_FILE ALLOC_FILE +VIEW_FILE FORMAT_FILE ENABLE_FILESYSTEM_TS_FALSE ENABLE_FILESYSTEM_TS_TRUE @@ -16190,7 +16190,7 @@ ac_compiler_gnu=$ac_cv_cxx_compiler_gnu ac_save_CXXFLAGS="$CXXFLAGS" - cat confdefs.h - <<_ACEOF >conftest.$ac_ext + cat confdefs.h - <<_ACEOF >conftest.$ac_ext /* end confdefs.h. */ #if ! defined __GCC_HAVE_SYNC_COMPARE_AND_SWAP_2 @@ -77463,11 +77463,6 @@ elf64) elfsize=64 ;; esac BACKTRACE_CPPFLAGS="$BACKTRACE_CPPFLAGS -DBACKTRACE_ELF_SIZE=$elfsize" - ALLOC_FILE=alloc.lo - - VIEW_FILE=read.lo - - { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether to build libbacktrace support" >&5 $as_echo_n "checking whether to build libbacktrace support... " >&6; } if test "$enable_libstdcxx_backtrace" == "auto"; then @@ -77475,7 +77470,55 @@ $as_echo_n "checking whether to build libbacktrace support... " >&6; } fi if test "$enable_libstdcxx_backtrace" == "yes"; then BACKTRACE_SUPPORTED=1 - BACKTRACE_USES_MALLOC=1 + + for ac_header in sys/mman.h +do : + ac_fn_c_check_header_mongrel "$LINENO" "sys/mman.h" "ac_cv_header_sys_mman_h" "$ac_includes_default" +if test "x$ac_cv_header_sys_mman_h" = xyes; then : + cat >>confdefs.h <<_ACEOF +#define HAVE_SYS_MMAN_H 1 +_ACEOF + +fi + +done + + case "${host}" in + *-*-msdosdjgpp) # DJGPP has sys/man.h, but no mmap + have_mmap=no ;; + *-*-*) + have_mmap="$ac_cv_header_sys_mman_h" ;; + esac + + if test "$have_mmap" = "no"; then + VIEW_FILE=read.lo + ALLOC_FILE=alloc.lo + else + VIEW_FILE=mmapio.lo + cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ + + #include <sys/mman.h> + #if !defined(MAP_ANONYMOUS) && !defined(MAP_ANON) + #error no MAP_ANONYMOUS + #endif + +_ACEOF +if ac_fn_c_try_cpp "$LINENO"; then : + ALLOC_FILE=mmap.lo +else + ALLOC_FILE=alloc.lo +fi +rm -f conftest.err conftest.i conftest.$ac_ext + fi + + + + BACKTRACE_USES_MALLOC=0 + if test "$ALLOC_FILE" = "alloc.lo"; then + BACKTRACE_USES_MALLOC=1 + fi + if test "$ac_has_gthreads" = "yes"; then BACKTRACE_SUPPORTS_THREADS=1 else
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