prevent perror from clobbering stderr's orientation

this requirement is specified by POSIX.

diff --git a/src/stdio/perror.c b/src/stdio/perror.c
index fdcb4d71c8855201c8a67858e8fa607fff038744..d0943f26a938bd9dad153c1d64dd88f643c31097 100644 (file)
--- a/src/stdio/perror.c
+++ b/src/stdio/perror.c
@@ -9,6 +9,11 @@ void perror(const char *msg)
        char *errstr = strerror(errno);
 
        FLOCK(f);
+
+       /* Save stderr's orientation and encoding rule, since perror is not
+        * permitted to change them. */
+       void *old_locale = f->locale;
+       int old_mode = f->mode;
        
        if (msg && *msg) {
                fwrite(msg, strlen(msg), 1, f);
@@ -18,5 +23,8 @@ void perror(const char *msg)
        fwrite(errstr, strlen(errstr), 1, f);
        fputc('\n', f);
 
+       f->mode = old_mode;
+       f->locale = old_locale;
+
        FUNLOCK(f);
 }