[PATCH v5] newlib: libc: Fix crash on fprintf to a wide-oriented stream.

[Christophe Lyon]

Hi!

On Thu, 9 Nov 2023 at 16:36, Takashi Yano <takashi.yano@nifty.ne.jp> wrote:
>
> On Thu, 9 Nov 2023 13:49:41 +0100
> Corinna Vinschen wrote:
> > On Nov  9 19:26, Takashi Yano wrote:
> > > On Thu, 9 Nov 2023 11:08:03 +0100
> > > Corinna Vinschen wrote:
> > > > Looks good, please push.
> > >
> > > Thanks. Should this also be applied to cygwin-3_4-branch?
> >
> > Tricky question.  It's a bugfix, yeah, but a bugfix for an undefined
> > situation.  And it's also a behavioral change.  So, from my POV we
> > shouldn't backport it.
>
> I see. I'll push it only for master branch.
>
> > But if you have another POV, we can discuss it.  It occured to me that
> > you didn't mention where the testcase is coming from.  Was that a
> > real-world problem?  If so, where and in which circumstances?
>
> No. It was discovered by an accidental mistake while writing
> a test case for another problem.
>

After this patch, our automated CI has detected regressions on arm-none-eabi
with GCC configured with:
--disable-multilib --with-mode=thumb --with-cpu=cortex-m33 --with-float=hard
(all these options are probably not mandatory, we have other
configurations pending in the build queue)

The regressions appear in the libstdc++ tests:
Running libstdc++:libstdc++-dg/conformance.exp ...
FAIL: 27_io/objects/wchar_t/12048-1.cc -std=gnu++17 execution test
FAIL: 27_io/objects/wchar_t/12048-2.cc -std=gnu++17 execution test
FAIL: 27_io/objects/wchar_t/12048-3.cc -std=gnu++17 execution test
FAIL: 27_io/objects/wchar_t/12048-4.cc -std=gnu++17 execution test
XPASS: 27_io/objects/wchar_t/12048-5.cc -std=gnu++17 execution test
FAIL: ext/stdio_sync_filebuf/wchar_t/1.cc -std=gnu++17 execution test
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-1.cc -std=gnu++17 execution test
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-2.cc -std=gnu++17 execution test
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-3.cc -std=gnu++17 execution test
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-4.cc -std=gnu++17 execution test

the logs show:
/libstdc++-v3/testsuite/27_io/objects/wchar_t/12048-1.cc:37: void
test01(): Assertion 'std::wcin.good()' failed.
FAIL: 27_io/objects/wchar_t/12048-1.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/27_io/objects/wchar_t/12048-2.cc:34: void
test01(): Assertion 'std::wcin.good()' failed.
FAIL: 27_io/objects/wchar_t/12048-2.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/27_io/objects/wchar_t/12048-3.cc:34: void
test01(): Assertion 'std::wcin.rdbuf()->sgetn(buf, 2) == 2' failed.
FAIL: 27_io/objects/wchar_t/12048-3.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/27_io/objects/wchar_t/12048-4.cc:31: void
test01(): Assertion 'std::wcin.rdbuf()->sgetn(buf, 2) == 2' failed.
FAIL: 27_io/objects/wchar_t/12048-4.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/ext/stdio_sync_filebuf/wchar_t/1.cc:43: void
test01(): Assertion 'traits_type::to_char_type(wsbuf.sgetc()) ==
w_lit[0]' failed.
FAIL: ext/stdio_sync_filebuf/wchar_t/1.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/ext/stdio_sync_filebuf/wchar_t/12948-1.cc:31:
void test02(): Assertion 'c1 != WEOF' failed.
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-1.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/ext/stdio_sync_filebuf/wchar_t/12948-2.cc:31:
void test03(): Assertion 'c1 != WEOF' failed.
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-2.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/ext/stdio_sync_filebuf/wchar_t/12948-3.cc:31:
void test04(): Assertion 'sbuf.sgetn(buf, 2) == 2' failed.
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-3.cc  -std=gnu++17 execution test
/libstdc++-v3/testsuite/ext/stdio_sync_filebuf/wchar_t/12948-4.cc:31:
void test05(): Assertion 'sbuf.sgetn(buf, 2) == 2' failed.
FAIL: ext/stdio_sync_filebuf/wchar_t/12948-4.cc  -std=gnu++17 execution test

I haven't dug further yet, does that ring a bell?

Thanks,

Christophe

> --
> Takashi Yano <takashi.yano@nifty.ne.jp>