[EXTERNAL] Re: GCC10 in sysroot: libstdc++ symbols

[Oleg Smolsky]

On 2021-03-11 10:01, Florian Weimer wrote:
> * Oleg Smolsky via Gcc-help:
>
>> Clearly the new build is not quite the same as the old one... but
>> which one is correct for Linux/x86-64? And what controls this
>> variance? It looks like glibc does not have a flag to control TLS any
>> more...
> You need to figure out why _GLIBCXX_HAVE_TLS was not detected at
> configure time.  See config/tls.m4.  There is likely something in
> config.log.

Thank you for the pointers, Florian and Jonathan!

I'm trying to figure out where the new build went awry. So far I have 
these crumbs:

$ find . -name config.log | xargs grep _TLS
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:set_have_cc_tls='-DHAVE_CC_TLS'
./gcc-build/gcc/config.log:configure:26862: checking assembler for 
R_386_TLS_GD_PLT reloc
./gcc-build/gcc/config.log:configure:26904: checking assembler for 
R_386_TLS_LDM_PLT reloc
./gcc-build/gcc/config.log:configure:26952: checking assembler for 
R_386_TLS_LDM reloc
./gcc-build/gcc/config.log:| #define HAVE_AS_TLS 1
./gcc-build/gcc/config.log:| #define HAVE_AS_IX86_TLSLDMPLT 0
./gcc-build/gcc/config.log:| #define HAVE_AS_IX86_TLSLDM 0
./gcc-build/gcc/config.log:| #define HAVE_AS_IX86_TLS_GET_ADDR_GOT 0
./gcc-build/gcc/config.log:| #define HAVE_AS_TLS 1
./gcc-build/gcc/config.log:| #define HAVE_AS_IX86_TLSLDMPLT 0
./gcc-build/gcc/config.log:| #define HAVE_AS_IX86_TLSLDM 0
./gcc-build/gcc/config.log:| #define HAVE_AS_IX86_TLS_GET_ADDR_GOT 0
./gcc-build/gcc/config.log:#define HAVE_AS_TLS 1
./gcc-build/gcc/config.log:#define HAVE_AS_IX86_TLSLDMPLT 0
./gcc-build/gcc/config.log:#define HAVE_AS_IX86_TLSLDM 0
./gcc-build/gcc/config.log:#define HAVE_AS_IX86_TLS_GET_ADDR_GOT 0

and

$ find . -name config.log | xargs grep tls
./gcc-build/x86_64-pc-linux-gnu/libgomp/config.log:configure:16001: 
checking whether the thread-local storage support is from emutls
./gcc-build/x86_64-pc-linux-gnu/libgomp/config.log:gcc_cv_have_tls=no
./gcc-build/x86_64-pc-linux-gnu/libgomp/config.log:gcc_cv_use_emutls=no
./gcc-build/x86_64-pc-linux-gnu/libstdc++-v3/config.log:gcc_cv_have_tls=no
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:configure:5460: 
checking whether the thread-local storage support is from emutls
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:gcc_cv_have_cc_tls=yes
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:gcc_cv_use_emutls=no
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:set_have_cc_tls='-DHAVE_CC_TLS'
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:set_use_emutls=''
./gcc-build/x86_64-pc-linux-gnu/libgcc/config.log:tmake_file=' 
$(srcdir)/config/t-crtstuff-pic $(srcdir)/config/t-libgcc-pic 
$(srcdir)/config/t-eh-dw2-dip $(srcdir)/config/t-slibgcc 
$(srcdir)/config/t-slibgcc-gld $(srcdir)/config/t-slibgcc-elf-ver 
$(srcdir)/config/t-linux $(srcdir)/config/i386/t-crtpc 
$(srcdir)/config/t-crtfm $(srcdir)/config/i386/t-crtstuff 
$(srcdir)/config/t-dfprules $(srcdir)/config/i386/t-cpuinfo 
$(srcdir)/config/t-tls $(srcdir)/config/i386/t-linux 
$(srcdir)/config/i386/t-msabi $(srcdir)/config/t-slibgcc-libgcc 
$(srcdir)/config/t-stack $(srcdir)/config/i386/t-stack-i386 
$(srcdir)/config/t-softfp-tf $(srcdir)/config/i386/t-softfp 
$(srcdir)/config/t-softfp $(srcdir)/config/i386/64/t-softfp-compat'
./gcc-build/x86_64-pc-linux-gnu/libitm/config.log:gcc_cv_have_tls=no

./gcc-build/gcc/config.log:configure:27105: checking assembler for 
calling ___tls_get_addr via GOT
./gcc-build/gcc/config.log:gcc_cv_as_ix86_tls_get_addr_via_got=no

That last one does an "as" check... Is that the trigger?

Thanks!
Oleg.