Add tests for stcncpy

include/string.h

@@ -104,8 +104,13 @@ __access(write_only, 1)
 __access(read_only, 2, 3)
 _FORTIFY_FN(stpncpy) char *stpncpy(char *__d, const char *__s, size_t __n)
 {
-	size_t __b = __bos(__d, 0);
+	/* trap if pointers are overlapping but not if dst == src.
+	 * gcc seems to like to generate code that relies on dst == src */
+	if ((__d < __s && __d + __n > __s) ||
+	    (__s < __d && __s + __n > __d))
+		__builtin_trap();
 
+	size_t __b = __bos(__d, 0);
 	if (__n > __b && strlen(__s) + 1 > __b)
 		__builtin_trap();
 	return __orig_stpncpy(__d, __s, __n);

tests/Makefile

@@ -22,6 +22,9 @@ TARGETS=test_memcpy_static_write     \
 	test_strncpy_overwrite_over  \
 	test_strncpy_overwrite_under \
 	test_strncpy_static_write    \
+	test_stpncpy_overwrite_over  \
+	test_stpncpy_overwrite_under \
+	test_stpncpy_static_write    \
 	test_getcwd                  \
 
 .SILENT:

tests/test_stpncpy_overwrite_over.c

@@ -0,0 +1,15 @@
+#include "common.h"
+
+#include <string.h>
+
+int main(int argc, char** argv) {
+  char buffer[9] = {'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', '\0'};
+  puts(buffer);
+
+  CHK_FAIL_START
+  stpncpy(buffer+1, buffer, 5);
+  CHK_FAIL_END
+
+  puts(buffer);
+  return ret;
+}

tests/test_stpncpy_overwrite_under.c

@@ -0,0 +1,15 @@
+#include "common.h"
+
+#include <string.h>
+
+int main(int argc, char** argv) {
+  char buffer[9] = {'A', 'A', 'A', 'A', 'B', 'B', 'B', 'B', '\0'};
+  puts(buffer);
+
+  CHK_FAIL_START
+  stpncpy(buffer-1, buffer, 5);
+  CHK_FAIL_END
+
+  puts(buffer);
+  return ret;
+}

tests/test_stpncpy_static_write.c

@@ -0,0 +1,16 @@
+#include "common.h"
+
+#include <string.h>
+
+int main(int argc, char** argv) {
+  char buffer[8] = {0};
+  stpncpy(buffer, "1234567", 5);
+  puts(buffer);
+
+  CHK_FAIL_START
+  stpncpy(buffer, "1234567890", 10);
+  CHK_FAIL_END
+
+  puts(buffer);
+  return ret;
+}