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()`. 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".
This is my first time, and I'm not sure if I need to resubmit a patch.ಥ_ಥ
