Add compatibility function for fgets(3).

This patch adds the `tor_fgets()` function to our compatibility layer.

`tor_fgets()` adds an additional check for whether the error-bit have
been enabled for the given file stream, if that is the case and `errno`
is set to `EAGAIN` we make sure that we always return NULL.

Unfortunately `fgets(3)` behaves differently on different versions of
the C library.

See: https://bugs.torproject.org/21416
See: https://bugs.torproject.org/20988
This commit is contained in:
Alexander Færøy 2017-02-27 15:37:31 +01:00
parent a0a4f8ae5d
commit 498287b3c3
No known key found for this signature in database
GPG Key ID: E15081D5D3C3DB53
3 changed files with 45 additions and 0 deletions

4
changes/bug20988 Normal file
View File

@ -0,0 +1,4 @@
o Minor bugfixes (portability):
- Add Tor compatibility function for fgets(3) due to inconsistency of
returned values in different supported C libraries. This fixes unit test
failures reported on FreeBSD. Fixes bug 20988.

View File

@ -3476,6 +3476,45 @@ tor_getpass(const char *prompt, char *output, size_t buflen)
#endif
}
/** Read at most one less than the number of characters specified by
* <b>size</b> from the given <b>stream</b> and store it in <b>str</b>.
*
* Reading stops when a newline character is found or at EOF or error. If any
* characters are read and there's no error, a trailing NUL byte is appended to
* the end of <b>str</b>.
*
* Upon successful completion, this function returns a pointer to the string
* <b>str</b>. If EOF occurs before any characters are read the function will
* return NULL and the content of <b>str</b> is unchanged. Upon error, the
* function returns NULL and the caller must check for error using foef(3) and
* ferror(3).
*/
char *
tor_fgets(char *str, int size, FILE *stream)
{
char *ret;
/* Reset errno before our call to fgets(3) to avoid a situation where the
* caller is calling us again because we just returned NULL and errno ==
* EAGAIN, but when they call us again we will always return NULL because the
* error flag on the file handler remains set and errno is set to EAGAIN.
*/
errno = 0;
ret = fgets(str, size, stream);
/* FreeBSD, OpenBSD, Linux (glibc), and Linux (musl) seem to disagree about
* what to do in the given situation. We check if the stream has been flagged
* with an error-bit and return NULL in that situation if errno is also set
* to EAGAIN.
*/
if (ferror(stream) && errno == EAGAIN) {
return NULL;
}
return ret;
}
/** Return the amount of free disk space we have permission to use, in
* bytes. Return -1 if the amount of free space can't be determined. */
int64_t

View File

@ -740,6 +740,8 @@ STATIC int tor_ersatz_socketpair(int family, int type, int protocol,
ssize_t tor_getpass(const char *prompt, char *output, size_t buflen);
char *tor_fgets(char *str, int size, FILE *stream);
/* This needs some of the declarations above so we include it here. */
#include "compat_threads.h"