path: root/src/stdio/vfwprintf.c
diff options
authorRich Felker <>2014-12-17 03:08:53 -0500
committerRich Felker <>2014-12-17 03:08:53 -0500
commitd42269d7c85308abdbf8cee38b1a1097249eb38b (patch)
tree049cb8ff518affdb27c1e767b993081a0cd96536 /src/stdio/vfwprintf.c
parentda16224fc5fea45b307d9f0565c2adc92f9e1da0 (diff)
correctly handle write errors encountered by printf-family functions
previously, write errors neither stopped further output attempts nor caused the function to return an error to the caller. this could result in silent loss of output, possibly in the middle of output in the event of a non-permanent error. the simplest solution is temporarily clearing the error flag for the target stream, then suppressing further output when the error flag is set and checking/restoring it at the end of the operation to determine the correct return value. since the wide version of the code internally calls the narrow fprintf to perform some of its underlying operations, initial clearing of the error flag is suppressed when performing a narrow vfprintf on a wide-oriented stream. this is not a problem since the behavior of narrow operations on wide-oriented streams is undefined.
Diffstat (limited to 'src/stdio/vfwprintf.c')
1 files changed, 6 insertions, 1 deletions
diff --git a/src/stdio/vfwprintf.c b/src/stdio/vfwprintf.c
index c6400591..ebdff001 100644
--- a/src/stdio/vfwprintf.c
+++ b/src/stdio/vfwprintf.c
@@ -149,7 +149,7 @@ static void pop_arg(union arg *arg, int type, va_list *ap)
static void out(FILE *f, const wchar_t *s, size_t l)
- while (l--) fputwc(*s++, f);
+ while (l-- && !(f->flags & F_ERR)) fputwc(*s++, f);
static int getint(wchar_t **s) {
@@ -345,6 +345,7 @@ int vfwprintf(FILE *restrict f, const wchar_t *restrict fmt, va_list ap)
va_list ap2;
int nl_type[NL_ARGMAX] = {0};
union arg nl_arg[NL_ARGMAX];
+ int olderr;
int ret;
/* the copy allows passing va_list* even if va_list is an array */
@@ -356,7 +357,11 @@ int vfwprintf(FILE *restrict f, const wchar_t *restrict fmt, va_list ap)
f->mode |= f->mode+1;
+ olderr = f->flags & F_ERR;
+ f->flags &= ~F_ERR;
ret = wprintf_core(f, fmt, &ap2, nl_arg, nl_type);
+ if (f->flags & F_ERR) ret = -1;
+ f->flags |= olderr;
return ret;