Add a test for strncat

3 files changed, 19 insertions, 3 deletions

diff --git a/include/string.h b/include/string.h
index 9bf17a0..8737f97 100644
--- a/include/string.h
+++ b/include/string.h
@@ -151,13 +151,12 @@ __access (read_only, 2, 3)
 _FORTIFY_FN(strncat) char *strncat(char *__d, const char *__s, size_t __n)
 {
         size_t __b = __bos(__d, 0);
-        size_t __sl, __dl;
 
         if (__n > __b) {
-                __sl = strlen(__s);
-                __dl = strlen(__d);
+                size_t __sl = strlen(__s);
                 if (__sl > __n)
                         __sl = __n;
+                size_t __dl = strlen(__d);
                 if (__sl + __dl + 1 > __b)
                         __builtin_trap();
         }
diff --git a/tests/Makefile b/tests/Makefile
index 11718cc..dcfe22e 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -19,6 +19,7 @@ TARGETS=test_memcpy_static_write     \
         test_strcpy_overwrite_over   \
         test_strcpy_overwrite_under  \
         test_strcpy_static_write     \
+        test_strncat_static_write    \
         test_strncpy_overwrite_over  \
         test_strncpy_overwrite_under \
         test_strncpy_static_write    \
diff --git a/tests/test_strncat_static_write.c b/tests/test_strncat_static_write.c
new file mode 100644
index 0000000..9332adc
--- /dev/null
+++ b/tests/test_strncat_static_write.c
@@ -0,0 +1,16 @@
+#include "common.h"
+
+#include <string.h>
+
+int main(int argc, char** argv) {
+  char buffer[8] = {0};
+  strncat(buffer, "1234567", 5);
+  puts(buffer);
+
+  CHK_FAIL_START
+  strncat(buffer, "1234567890", 10);
+  CHK_FAIL_END
+
+  puts(buffer);
+  return ret;
+}