Re: [PATCH 2/2] libstdc++: Move stream initialization into compiled library [PR44952]

[Hans-Peter Nilsson <hp@axis.com>]

> From: Patrick Palka via Gcc-patches <gcc-patches@gcc.gnu.org>
> Date: Fri, 4 Nov 2022 16:05:25 +0100

> This patch moves the global object for constructing the standard streams
> out from <iostream> and into the compiled library on targets that support
> the init_priority attribute.  This means that <iostream> no longer
> introduces a separate global constructor in each TU that includes it.
> 
> We can do this only if the init_priority attribute is supported because
> we need to force that the stream initialization runs first before any
> user-defined global initializer in programs that that use a static
> libstdc++.a.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look right?
> Unfortunately I don't have access to a system that truly doesn't support
> init priorities, so I instead tested that situation by artificially
> disabling the init_priority attribute on x86_64.
> 
> 	PR libstdc++/44952
> 	PR libstdc++/98108
> 
> libstdc++-v3/ChangeLog:
> 
> 	* include/bits/c++config (_GLIBCXX_HAS_ATTRIBUTE): Define.
> 	(_GLIBCXX_HAVE_ATTRIBUTE_INIT_PRIORITY): Define.
> 	* include/std/iostream (__ioinit): Define only if init_priority
> 	attribute isn't usable.
> 	* src/c++98/ios_init.cc (__ioinit): Define here instead if
> 	the init_priority is usable.
> 	* src/c++98/ios_base_init.h: New file.

This (r13-3707-g4e4e3ffd10f53e) broke statically linked programs
using iostreams (affected embedded targets + "native" with
-static).  For me it manifests as adding some 100+ fails to my
cris-elf autotester also repeatable using a native Debian 11
x86_64 build running the test-suite with -static like "make
check-gcc-c++ 'RUNTESTFLAGS=--target_board=unix/-static
old-deja.exp=15071.C'".

I opened PR107701 for it.

brgds, H-P