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simplify/refactor fflush and make fflush_unlocked an alias for fflush 

previously, fflush_unlocked was an alias for an internal backend that
was called by fflush, either for its argument or in a loop for each
file if a null pointer was passed. since the logic for the latter was
in the main fflush function, fflush_unlocked crashed when passed a
null pointer, rather than flushing all open files. since
fflush_unlocked is not a standard function and has no specification,
it's not clear whether it should be expected to accept null pointers
like fflush does, but a reasonable argument could be made that it
should.

this patch eliminates the helper function, simplifying fflush, and
makes fflush_unlocked an alias for fflush, which is valid because the
two functions agree in their behavior in all cases where their
behavior is defined (the unlocked version has undefined behavior if
another thread could hold locks).
This commit is contained in:
Rich Felker 2016-09-18 21:45:47 -04:00
parent 5505f6afae
commit c002668eb0
1 changed files with 23 additions and 30 deletions
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53
src/stdio/fflush.c
View File

@ -1,11 +1,30 @@
#include "stdio_impl.h" #include "stdio_impl.h"
static int __fflush_unlocked(FILE *f) /* stdout.c will override this if linked */
static FILE *volatile dummy = 0;
weak_alias(dummy, __stdout_used);
int fflush(FILE *f)
{ {
if (!f) {
int r = __stdout_used ? fflush(__stdout_used) : 0;
for (f=*__ofl_lock(); f; f=f->next)
if (f->wpos > f->wbase) r |= fflush(f);
__ofl_unlock();
return r;
}
FLOCK(f);
/* If writing, flush output */ /* If writing, flush output */
if (f->wpos > f->wbase) { if (f->wpos > f->wbase) {
f->write(f, 0, 0); f->write(f, 0, 0);
if (!f->wpos) return EOF; if (!f->wpos) {
FUNLOCK(f);
return EOF;
}
} }
/* If reading, sync position, per POSIX */ /* If reading, sync position, per POSIX */
@ -15,34 +34,8 @@ static int __fflush_unlocked(FILE *f)
f->wpos = f->wbase = f->wend = 0; f->wpos = f->wbase = f->wend = 0;
f->rpos = f->rend = 0; f->rpos = f->rend = 0;
FUNLOCK(f);
return 0; return 0;
} }
/* stdout.c will override this if linked */ weak_alias(fflush, fflush_unlocked);
static FILE *volatile dummy = 0;
weak_alias(dummy, __stdout_used);
int fflush(FILE *f)
{
int r;
if (f) {
FLOCK(f);
r = __fflush_unlocked(f);
FUNLOCK(f);
return r;
}
r = __stdout_used ? fflush(__stdout_used) : 0;
for (f=*__ofl_lock(); f; f=f->next) {
FLOCK(f);
if (f->wpos > f->wbase) r |= __fflush_unlocked(f);
FUNLOCK(f);
}
__ofl_unlock();
return r;
}
weak_alias(__fflush_unlocked, fflush_unlocked);