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* [PATCH] libstdc++: Another attempt to ensure g++ 13+ compiled programs enforce gcc 13.2+ libstdc++.so.6 [PR108969]
@ 2023-04-28  7:34 Jakub Jelinek
  2023-04-28  8:35 ` Jonathan Wakely
  2023-05-02 11:20 ` Rainer Orth
  0 siblings, 2 replies; 5+ messages in thread
From: Jakub Jelinek @ 2023-04-28  7:34 UTC (permalink / raw)
  To: Jonathan Wakely, Patrick Palka; +Cc: gcc-patches, libstdc++, Rainer Orth

Hi!

GCC used to emit an instance of an empty ios_base::Init class in
every TU which included <iostream> to ensure it is std::cout etc.
is initialized, but thanks to Patrick work on some targets (which have
init_priority attribute support) it is now initialized only inside of
libstdc++.so.6/libstdc++.a.

This causes a problem if people do something that has never been supported,
try to run GCC 13 compiled C++ code against GCC 12 or earlier
libstdc++.so.6 - std::cout etc. are then never initialized because code
including <iostream> expects the library to initialize it and the library
expects code including <iostream> to do that.

The following patch is second attempt to make this work cheaply as the
earlier attempt of aliasing the std::cout etc. symbols with another symbol
version didn't work out due to copy relocation breaking the aliases appart.

The patch forces just a _ZSt21ios_base_library_initv undefined symbol
into all *.o files which include <iostream> and while there is no runtime
relocation against that, it seems to enforce the right version of
libstdc++.so.6.  /home/jakub/src/gcc/obj08i/usr/local/ is the install
directory of trunk patched with this patch, /home/jakub/src/gcc/obj06/
is builddir of trunk without this patch, system g++ is GCC 12.1.1.
$ cat /tmp/hw.C
#include <iostream>

int
main ()
{
  std::cout << "Hello, world!" << std::endl;
}
$ cd /home/jakub/src/gcc/obj08i/usr/local/bin
$ ./g++ -o /tmp/hw /tmp/hw.C
$ readelf -Wa /tmp/hw 2>/dev/null | grep initv
     4: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND _ZSt21ios_base_library_initv@GLIBCXX_3.4.32 (4)
    71: 0000000000000000     0 FUNC    GLOBAL DEFAULT  UND _ZSt21ios_base_library_initv@GLIBCXX_3.4.32
$ /tmp/hw
/tmp/hw: /lib64/libstdc++.so.6: version `GLIBCXX_3.4.32' not found (required by /tmp/hw)
$ LD_LIBRARY_PATH=/home/jakub/src/gcc/obj08i/usr/local/lib64/ /tmp/hw
Hello, world!
$ LD_LIBRARY_PATH=/home/jakub/src/gcc/obj06/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/ /tmp/hw
/tmp/hw: /home/jakub/src/gcc/obj06/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.6: version `GLIBCXX_3.4.32' not found (required by /tmp/hw)
$ g++ -o /tmp/hw /tmp/hw.C
$ /tmp/hw
Hello, world!
$ LD_LIBRARY_PATH=/home/jakub/src/gcc/obj06/x86_64-pc-linux-gnu/libstdc++-v3/src/.libs/ /tmp/hw
Hello, world!
$ LD_LIBRARY_PATH=/home/jakub/src/gcc/obj08i/usr/local/lib64/ /tmp/hw
Hello, world!

Bootstrapped/regtested on x86_64-linux, i686-linux and sparc-sun-solaris2.11

On the last one I've actually checked a version which had
defined(_GLIBCXX_SYMVER_SUN) next to defined(_GLIBCXX_SYMVER_GNU), but
init_priority attribute doesn't seem to be supported there and so I couldn't
actually test how this works there.  Using gas and Sun ld, Rainer, does one
need to use gas + gld for init_priority or something else?

Ok for trunk and after a while for GCC 13.2?

2023-04-28  Jakub Jelinek  <jakub@redhat.com>

	PR libstdc++/108969
	* config/abi/pre/gnu.ver (GLIBCXX_3.4.32): Export
	_ZSt21ios_base_library_initv.
	* testsuite/util/testsuite_abi.cc (check_version): Add GLIBCXX_3.4.32
	symver and make it the latestp.
	* src/c++98/ios_init.cc (ios_base_library_init): New alias.
	* acinclude.m4 (libtool_VERSION): Change to 6:32:0.
	* include/std/iostream: If init_priority attribute is supported
	and _GLIBCXX_SYMVER_GNU, force undefined _ZSt21ios_base_library_initv
	symbol into the object.
	* configure: Regenerated.

--- libstdc++-v3/config/abi/pre/gnu.ver.jj	2023-04-20 09:36:09.415371050 +0200
+++ libstdc++-v3/config/abi/pre/gnu.ver	2023-04-27 17:58:44.599675359 +0200
@@ -2514,6 +2514,10 @@ GLIBCXX_3.4.31 {
 
 } GLIBCXX_3.4.30;
 
+GLIBCXX_3.4.32 {
+    _ZSt21ios_base_library_initv;
+} GLIBCXX_3.4.31;
+
 # Symbols in the support library (libsupc++) have their own tag.
 CXXABI_1.3 {
 
--- libstdc++-v3/testsuite/util/testsuite_abi.cc.jj	2023-01-16 11:52:17.495713257 +0100
+++ libstdc++-v3/testsuite/util/testsuite_abi.cc	2023-04-27 17:30:39.651173917 +0200
@@ -213,6 +213,7 @@ check_version(symbol& test, bool added)
       known_versions.push_back("GLIBCXX_LDBL_3.4.29");
       known_versions.push_back("GLIBCXX_3.4.30");
       known_versions.push_back("GLIBCXX_3.4.31");
+      known_versions.push_back("GLIBCXX_3.4.32");
       known_versions.push_back("GLIBCXX_LDBL_3.4.31");
       known_versions.push_back("GLIBCXX_IEEE128_3.4.29");
       known_versions.push_back("GLIBCXX_IEEE128_3.4.30");
@@ -251,7 +252,7 @@ check_version(symbol& test, bool added)
 	test.version_status = symbol::incompatible;
 
       // Check that added symbols are added in the latest pre-release version.
-      bool latestp = (test.version_name == "GLIBCXX_3.4.31"
+      bool latestp = (test.version_name == "GLIBCXX_3.4.32"
 	  // XXX remove next 2 lines when baselines have been regenerated.
 		     || test.version_name == "GLIBCXX_IEEE128_3.4.31"
 		     || test.version_name == "GLIBCXX_LDBL_3.4.31"
--- libstdc++-v3/src/c++98/ios_init.cc.jj	2023-01-16 11:52:16.995720625 +0100
+++ libstdc++-v3/src/c++98/ios_init.cc	2023-04-27 18:34:46.121276617 +0200
@@ -199,5 +199,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
     return __ret;
   }
 
+#ifdef _GLIBCXX_SYMVER_GNU
+  void ios_base_library_init (void)
+  __attribute__((alias ("_ZNSt8ios_base4InitC1Ev")));
+#endif
+
 _GLIBCXX_END_NAMESPACE_VERSION
 } // namespace
--- libstdc++-v3/acinclude.m4.jj	2023-02-02 09:53:31.745525704 +0100
+++ libstdc++-v3/acinclude.m4	2023-04-27 17:27:51.071626279 +0200
@@ -3841,7 +3841,7 @@ changequote([,])dnl
 fi
 
 # For libtool versioning info, format is CURRENT:REVISION:AGE
-libtool_VERSION=6:31:0
+libtool_VERSION=6:32:0
 
 # Everything parsed; figure out what files and settings to use.
 case $enable_symvers in
--- libstdc++-v3/include/std/iostream.jj	2023-01-16 11:52:16.968721023 +0100
+++ libstdc++-v3/include/std/iostream	2023-04-27 18:34:07.479837226 +0200
@@ -77,6 +77,8 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
   // in the compiled library instead (src/c++98/globals_io.cc).
 #if !__has_attribute(__init_priority__)
   static ios_base::Init __ioinit;
+#elif defined(_GLIBCXX_SYMVER_GNU)
+  __extension__ __asm (".globl _ZSt21ios_base_library_initv");
 #endif
 
 _GLIBCXX_END_NAMESPACE_VERSION
--- libstdc++-v3/configure.jj	2023-02-02 09:53:31.795524981 +0100
+++ libstdc++-v3/configure	2023-04-27 17:29:13.263429963 +0200
@@ -68652,7 +68652,7 @@ $as_echo "$as_me: WARNING: === Symbol ve
 fi
 
 # For libtool versioning info, format is CURRENT:REVISION:AGE
-libtool_VERSION=6:31:0
+libtool_VERSION=6:32:0
 
 # Everything parsed; figure out what files and settings to use.
 case $enable_symvers in

	Jakub


^ permalink raw reply	[flat|nested] 5+ messages in thread
end of thread, other threads:[~2023-05-02 15:43 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
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2023-04-28  7:34 [PATCH] libstdc++: Another attempt to ensure g++ 13+ compiled programs enforce gcc 13.2+ libstdc++.so.6 [PR108969] Jakub Jelinek
2023-04-28  8:35 ` Jonathan Wakely
2023-04-28 22:02   ` Jakub Jelinek
2023-05-02 15:43     ` Jonathan Wakely
2023-05-02 11:20 ` Rainer Orth

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