On Wed, 24 Dec 2025 at 17:01, 王靖淏 <[email protected]> wrote:
>
> On Mon, Dec 22, 2025 at 4:37 AM Jonathan Wakely <[email protected]> wrote:
> >
> >
> >
> > On Sun, 21 Dec 2025, 19:44 Wang Jinghao, <[email protected]> wrote:
> >>
> >> Ignoring FORMAT_MESSAGE_IGNORE_INSERTS when retrieving system
> >> error messages from FormatMessage may result in unexpected error messages
> >> and
> >> trigger new exceptions.
> >
> >
> > For those like me who have no idea what this is about, this explains it:
> > https://devblogs.microsoft.com/oldnewthing/20071128-00/?p=24353
> >
> > Can we add a test with error code 87?
> I discovered that `std::local` does not affect the language used by
> the system error information obtained by `FormatMessage`. It seems
> that `void test3()` in
> `libstdc++-v3\testsuite\19_diagnostics\error_category\system_category.cc`
> cannot pass errors in non-English language environments.
> >
> >
> >> This patch changes the
> >> std::system_category.message(int) to be the same as the flags in
> >> gcc/plugin.cc:win32_error_msg()
> >>
> >> libstdc++-v3/ChangeLog:
> >>
> >> * src/c++11/system_error.cc:
> >
> >
> > This changelog entry is missing a description.
> I'am sorry I forgot. ; (
>
> libstdc++-v3/ChangeLog:
>
> * src/c++11/system_error.cc (std::system_category): Add flag
> FORMAT_MESSAGE_IGNORE_INSERTS and
> FORMAT_MESSAGE_MAX_WIDTH_MASK to
> dwFlag parameter of the FormatMessage function.
>
> >> ---
> >> libstdc++-v3/src/c++11/system_error.cc | 4 +++-
> >> 1 file changed, 3 insertions(+), 1 deletion(-)
> >>
> >> diff --git a/libstdc++-v3/src/c++11/system_error.cc
> >> b/libstdc++-v3/src/c++11/system_error.cc
> >> index b9a0b2c158f..ea7b5cd1226 100644
> >> --- a/libstdc++-v3/src/c++11/system_error.cc
> >> +++ b/libstdc++-v3/src/c++11/system_error.cc
> >> @@ -162,7 +162,9 @@ namespace
> >> char* buf = nullptr;
> >> auto len
> >> = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM
> >> - | FORMAT_MESSAGE_ALLOCATE_BUFFER,
> >> + | FORMAT_MESSAGE_ALLOCATE_BUFFER
> >> + | FORMAT_MESSAGE_IGNORE_INSERTS
> >> + | FORMAT_MESSAGE_MAX_WIDTH_MASK,
> >> nullptr,
> >> i,
> >> LANG_USER_DEFAULT,
> >> --
> >> 2.52.0
> >>
>
> I found that the existing `test03` function in
> `libstdc++-v3/src/c++11/system_error.cc`, used for testing
> `std::system_error_category.message(int)`, doesn't work correctly in
> non-English language environments. This is likely because neither
> `std::locale` nor `std::setlocale` affects the language of the error
> message obtained by `FormatMessage()`.
We pass LANG_USER_DEFAULT to FormatMessage, but I don't think that is
related in any way to the C locale.
I think the testcase could use SetThreadPreferredUILanguages to set
en-US as the language that will be used by FormatMessage.
> Furthermore, in non-English
> environments, such as Chinese, system error messages end with "."\r\n"
> instead of ".\r\n", which prevents `__builtin_memcmp(buf + len - 3,
> ".\r\n", 3) {in libstdc++-v3\src\c++11\system_error.cc:178}` from
> correctly removing the trailing "\r\n".
Let's do this instead:
if (len > 2 && !__builtin_memcmp(buf + len - 2, "\r\n", 2)) [[likely]]
len -= 2 + (buf[len - 1] == '.');
>
> This is my first time, and I'm not sure if I need to resubmit a patch.ಥ_ಥ
