Hello,
Attempting to port abseil source package to the GNU/Hurd I found some
weird behaviour in the strerror_r function call when errnum is -1.
#include <stdio.h>
#include <string.h>
int main(int argc, char **argv)
{
char buf[100] = {0};
strerror_r(-1, buf, 100);
printf("strerror_r: %s\n", buf);
return 0;
}
This is my simplified reproducer. When I run it on Debian GNU/Linux
it outputs the following string:
strerror_r: Unknown error -1
However, when running in GNU/Hurd, the output is a bit different:
strerror_r: Error in unknown error system: FFFFFFFF
That difference makes the abseil test suite to produce an error
in the following test[1]:
TEST(StrErrorTest, InvalidErrorCode) {
errno = ERANGE;
EXPECT_THAT(absl::base_internal::StrError(-1),
AnyOf(Eq("No error information"), Eq("Unknown error -1")));
EXPECT_THAT(errno, Eq(ERANGE));
}
The POSIX specification says that an unknown error shall be indicated[2]:
[CX] [Option Start] If the value of errnum is a valid error number, the
message string shall indicate what error occurred; if the value of
errnum is zero, the message string shall either be an empty string or
indicate that no error occurred; otherwise, if these functions complete
successfully, the message string shall indicate that an unknown error
occurred. [Option End]
One could argue that the requirement is fullfilled, the message says
`unknown error` after all :-) But aligning to what GNU/Linux does would
help the porting to be easier.
What should we do here?
Regards,
Diego
--
[1]
https://github.com/abseil/abseil-cpp/blob/master/absl/base/internal/strerror_test.cc#L41
[2] https://pubs.opengroup.org/onlinepubs/9799919799/functions/strerror.html
