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stdio: implement flockfile, ftrylockfile, funlockfile #477

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stdio: implement flockfile, ftrylockfile, funlockfile #477

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58f362b
stdio: implement flockfile, ftrylockfile, funlockfile
julianuziemblo May 21, 2026
e3f29f7
stdio/fopen: set errno properly
julianuziemblo May 22, 2026
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5 changes: 5 additions & 0 deletions include/stdio.h
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Original file line number Diff line number Diff line change
Expand Up @@ -370,6 +370,11 @@ extern void _file_init(void);

/* stdio locking functions */
extern void flockfile(FILE *stream);


extern int ftrylockfile(FILE *stream);


extern void funlockfile(FILE *stream);


Expand Down
47 changes: 40 additions & 7 deletions stdio/file.c
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Expand Up @@ -47,6 +47,11 @@ typedef struct {
} popen_FILE;


static const struct lockAttr flockAttr = {
.type = PH_LOCK_RECURSIVE
};


FILE *stdin, *stdout, *stderr;


Expand Down Expand Up @@ -185,28 +190,41 @@ FILE *fopen(const char *filename, const char *mode)
int m;
FILE *f;
int fd;
int err;

if ((m = string2mode(mode)) < 0) {
errno = EINVAL;
return NULL;
}

if ((fd = __safe_open(filename, m, DEFFILEMODE)) < 0) {
/* errno set by open */
return NULL;
}

if ((f = calloc(1, sizeof(FILE))) == NULL) {
err = errno;
__safe_close(fd);
errno = err;
return NULL;
}

if ((f->buffer = buffAlloc(BUFSIZ)) == NULL) {
err = errno;
__safe_close(fd);
free(f);
errno = err;
return NULL;
}

if ((err = mutexCreateWithAttr(&f->lock, &flockAttr)) < 0) {
buffFree(f->buffer, BUFSIZ);
__safe_close(fd);
free(f);
errno = abs(err);
return NULL;
}

mutexCreate(&f->lock);
f->bufsz = BUFSIZ;
f->fd = fd;
f->mode = m;
Expand All @@ -221,7 +239,7 @@ FILE *fopen(const char *filename, const char *mode)

FILE *fdopen(int fd, const char *mode)
{
int m, fdm;
int m, fdm, err;
FILE *f;

if ((m = string2mode(mode)) < 0) {
Expand Down Expand Up @@ -249,7 +267,14 @@ FILE *fdopen(int fd, const char *mode)
return NULL;
}

mutexCreate(&f->lock);
mutexCreateWithAttr(&f->lock, &flockAttr);
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if ((err = mutexCreateWithAttr(&f->lock, &flockAttr)) < 0) {
buffFree(f->buffer, BUFSIZ);
free(f);
errno = abs(err);
return NULL;
}

f->bufsz = BUFSIZ;
f->fd = fd;
f->mode = m;
Expand Down Expand Up @@ -1300,7 +1325,7 @@ FILE *popen(const char *command, const char *mode)
goto failed;
}

if (mutexCreate(&pf->file.lock) < 0) {
if (mutexCreateWithAttr(&pf->file.lock, &flockAttr) < 0) {
pf->file.lock = 0;
goto failed;
}
Expand Down Expand Up @@ -1401,16 +1426,16 @@ void _file_init(void)
stdout->bufsz = BUFSIZ;

stdin->bufeof = stdin->bufpos = BUFSIZ;
mutexCreate(&stdin->lock);
mutexCreateWithAttr(&stdin->lock, &flockAttr);

stdout->bufpos = 0;
stdout->flags = F_WRITING;
mutexCreate(&stdout->lock);
mutexCreateWithAttr(&stdout->lock, &flockAttr);

stderr->buffer = NULL;
stderr->bufsz = 0;
stderr->flags = F_WRITING;
mutexCreate(&stderr->lock);
mutexCreateWithAttr(&stderr->lock, &flockAttr);

if (isatty(stdout->fd)) {
stdout->flags |= F_LINE;
Expand All @@ -1428,11 +1453,19 @@ void _file_init(void)

void flockfile(FILE *file)
{
mutexLock(file->lock);
}


int ftrylockfile(FILE *file)
{
return mutexTry(file->lock);
}


void funlockfile(FILE *file)
{
mutexUnlock(file->lock);
}


Expand Down
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