Re: libstdc++/2907: libstdc++ compiled with optimization fails to initialize ios.

[Carlo Wood <carlo at alinoe dot com>]

After compiling as above, and using the given test program that links
directly with the compiled (not installed) libstdc++:

~/c++/libcw/src/libcwd/testsuite>ldd a.out
        librmalloc.so.1 => /home/carlo/c++/rmalloc/librmalloc.so.1 (0x40018000)
        libstdc++.so.3 => /usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src/.libs/libstdc++.so.3 (0x4001d000)
        libm.so.6 => /lib/libm.so.6 (0x4015d000)
        libgcc_s.so.0 => /usr/src/gcc/gcc-objdir-3.0/gcc/libgcc_s.so.0 (0x4017e000)
        libc.so.6 => /lib/libc.so.6 (0x40188000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

in a different environment (not affecting the environment where I am compiling the
stdc++ library) (note that rmalloc is used to make sure there is no memory corruption
involved), I did the following tests:

/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src>grep '^CXXFLAGS =' Makefile
CXXFLAGS = -O9 -march=pentiumpro -fomit-frame-pointer -D_GNU_SOURCE
~/c++/libcw/src/libcwd/testsuite>a.out 2> /dev/null
Segmentation fault (core dumped)

/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src>vi Makefile
/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src>grep '^CXXFLAGS =' Makefile
CXXFLAGS = -O9 -D_GNU_SOURCE
/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src>rm *.lo *.o
/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src>make > /dev/null
~/c++/libcw/src/libcwd/testsuite>a.out 2> /dev/null
~/c++/libcw/src/libcwd/testsuite>

Conclusion: the problem is either -march=pentiumpro or -fomit-frame-pointer

And so on...

CXXFLAGS in src/Makefile	  result

-O9 -march=pentiumpro		: no core
-fomit-frame-pointer		: no core
-O9 -fomit-frame-pointer	: core
-O2 -fomit-frame-pointer	: core
-O -fomit-frame-pointer		: core
-fomit-frame-pointer		: no core

Next I started to compile the files one by one with -O -fomit-frame-pointer.

basic_file			: no core
bitset				: no core
c++locale			: no core
codecvt				: no core
complex_io			: no core
functexcept			: no core
globals				: no core
ios				: no core
limitsMEMBERS			: no core
locale-inst			: no core
locale				: core

Next I compiled all files with -O -fomit-frame-pointer *except* locale.cc, this
gave no core.  Finally I recompiled all files with -O9 -march=pentiumpro -fomit-frame-pointer
except locale.cc, which was compiled with nothing.  This still resulted in no core.

Conclusion, the problem is compiling locale.cc with -O -fomit-frame-pointer.

Next I started to use different options instead of -O for locale.lo, the rest still
compiled with -O9 -march=pentiumpro -fomit-frame-pointer.

CXXFLAGS in src/Makefile				  result

							: no core
-O -fomit-frame-pointer					: core
-fthread-jumps -fdefer-pop -fomit-frame-pointer 	: core
-fomit-frame-pointer 					: no core
-fdefer-pop -fomit-frame-pointer 			: core
-fthread-jumps -fomit-frame-pointer 			: no core


Final conclusion: The problem shows itself when compiling locale.cc with
 "-fdefer-pop -fomit-frame-pointer", or to be exact:

/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src>make
/bin/sh ../libtool --tag CXX --mode=compile /usr/src/gcc/gcc-objdir-3.0/gcc/xgcc \
	 -B/usr/src/gcc/gcc-objdir-3.0/gcc/ -nostdinc++  -L/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src \
	-L/usr/src/gcc/gcc-objdir-3.0/i686-pc-linux-gnu/libstdc++-v3/src/.libs -B/usr/local/gcc-3.0/i686-pc-linux-gnu/bin/ \
	-B/usr/local/gcc-3.0/i686-pc-linux-gnu/lib/ -isystem /usr/local/gcc-3.0/i686-pc-linux-gnu/include -nostdinc++  \
	-I/usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/include -I/usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/include/std \
	-I/usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/include/c_std -I../include \
	-I/usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/libsupc++ -I../libio -I/usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/libio \
	-I/usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/libmath \
        -fthread-jumps -fomit-frame-pointer -D_GNU_SOURCE \
        -fno-implicit-templates           -Wall -Wno-format -W -Wwrite-strings -Winline  -fdiagnostics-show-location=once \
	-ffunction-sections -fdata-sections  -g    -c /usr/src/gcc/gcc-cvs-3.0/libstdc++-v3/src/locale.cc

--
Carlo Wood <carlo@alinoe.com>