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authorZack Weinberg <zackw@panix.com>2017-04-01 10:17:44 -0400
committerZack Weinberg <zackw@panix.com>2017-04-07 07:48:57 -0400
commit544ce845def4540de11d9484df888df94876b14e (patch)
treedbd8eae480b47ab43e70bafb636a83c1963abb86 /include
parent7e161bef0bc9d5ea5e6f3dd490ecd5da6f642671 (diff)
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getopt: clean up error reporting
getopt can print a whole bunch of error messages, and when used standalone (from gnulib) it uses fprintf to do that. But fprintf is a cancellation point and getopt isn't, and also applying fprintf to a stream in wide-character mode is not allowed. glibc has an internal function called __fxprintf that writes a narrow format string to a stream regardless of mode, but it only handles ASCII format strings, and it's still a cancellation point. getopt's messages are translated, so they might not be ASCII. So getopt has an error message to an asprintf buffer, monkeys with internal flag bits on stderr to disable cancellation, and then calls __fxprintf(stderr, "%s", buffer). There isn't even a helper function, the code is duplicated every time. This patch fixes __fxprintf to handle arbitrary multibyte format strings, and adds a variant __fxprintf_nocancel that does the same thing but also isn't a cancellation point. (It still _works_ by monkeying with internal flag bits on the FILE, but that's not really a layering violation for code in stdio-common.) All of the #ifdef _LIBC blocks can then be reduced to their standalone versions with a little help from some macros at the top of the file. I also wrote a test case to verify that getopt really isn't a cancellation point, and I'm glad I did, because it found two bugs, one of which wasn't even to do with cancellation (see previous patch). * stdio-common/fxprintf.c (__fxprintf_nocancel): New function. (locked_vfxprintf): New helper function. Handle arbitrary multibyte strings, not just ASCII. * include/stdio.h: Declare __fxprintf_nocancel. * posix/getopt.c: When _LIBC is defined, define fprintf to __fxprintf_nocancel, flockfile to _IO_flockfile, and funlockfile to _IO_funlockfile. When neither _LIBC nor _POSIX_THREAD_SAFE_FUNCTIONS is defined, define flockfile and funlockfile as no-ops. (_getopt_internal_r): Remove all internal #ifdef _LIBC blocks; the standalone error-printing code can now be used for libc as well. Add an flockfile/funlockfile pair around one case where the error message is printed in several chunks. Don't use fputc. * posix/tst-getopt-cancel.c: New test. * posix/Makefile: Run it.
Diffstat (limited to 'include')
-rw-r--r--include/stdio.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/stdio.h b/include/stdio.h
index 17b5a05..4e7cfa1 100644
--- a/include/stdio.h
+++ b/include/stdio.h
@@ -114,6 +114,8 @@ extern wint_t __getwc_unlocked (FILE *__fp);
extern int __fxprintf (FILE *__fp, const char *__fmt, ...)
__attribute__ ((__format__ (__printf__, 2, 3)));
+extern int __fxprintf_nocancel (FILE *__fp, const char *__fmt, ...)
+ __attribute__ ((__format__ (__printf__, 2, 3)));
extern const char *const _sys_errlist_internal[] attribute_hidden;
extern int _sys_nerr_internal attribute_hidden;