make strerror_r behave nicer on failure

if the buffer is too short, at least return a partial string. this is
helpful if the caller is lazy and does not check for failure. care is
taken to avoid writing anything if the buffer length is zero, and to
always null-terminate when the buffer length is non-zero.

diff --git a/src/string/strerror_r.c b/src/string/strerror_r.c
index 6fdd4ce2c844530222a974d3b543a002bec4e04c..907dcf079a9a39c977ef52523c4fb564676f5217 100644 (file)
--- a/src/string/strerror_r.c
+++ b/src/string/strerror_r.c
@@ -4,8 +4,14 @@
 int strerror_r(int err, char *buf, size_t buflen)
 {
        char *msg = strerror(err);
-       if (strlen(msg) >= buflen)
+       size_t l = strlen(msg);
+       if (l >= buflen) {
+               if (buflen) {
+                       memcpy(buf, msg, buflen-1);
+                       buf[buflen-1] = 0;
+               }
                return ERANGE;
-       strcpy(buf, msg);
+       }
+       memcpy(buf, msg, l+1);
        return 0;
 }