X-Git-Url: https://pd.if.org/git/?a=blobdiff_plain;f=functions%2Fstring%2Fstrncpy.c;h=efb6480468391a0bf35fae0e8001bee7d0d5c1d9;hb=b189506b1b895940933bdfc5d6d6ae5d0ba65721;hp=91f97da3d28f39e9d15a8d6e7380b9c38ee97120;hpb=b08f4b52b1cd1f7a9553c0f357a7c90859fa3e73;p=pdclib

diff --git a/functions/string/strncpy.c b/functions/string/strncpy.c
index 91f97da..efb6480 100644
--- a/functions/string/strncpy.c
+++ b/functions/string/strncpy.c
@@ -16,11 +16,13 @@ char * strncpy( char * _PDCLIB_restrict s1, const char * _PDCLIB_restrict s2, si
     while ( ( n > 0 ) && ( *s1++ = *s2++ ) )
     {
         /* Cannot do "n--" in the conditional as size_t is unsigned and we have
-        to check it again for >0 in the next loop.
+           to check it again for >0 in the next loop below, so we must not risk
+           underflow.
         */
         --n;
     }
-    while ( --n )
+    /* Checking against 1 as we missed the last --n in the loop above. */
+    while ( n-- > 1 )
     {
         *s1++ = '\0';
     }
@@ -45,6 +47,10 @@ int main( void )
     TESTCASE( s[6] == 'x' );
     TESTCASE( strncpy( s, abcde, 7 ) == s );
     TESTCASE( s[6] == '\0' );
+    TESTCASE( strncpy( s, "xxxx", 3 ) == s );
+    TESTCASE( s[0] == 'x' );
+    TESTCASE( s[2] == 'x' );
+    TESTCASE( s[3] == 'd' );
     return TEST_RESULTS;
 }
 #endif