tests: Make strndup(3) available to C99

expat/tests/common.c

@@ -42,6 +42,8 @@
 */
 
 #include <assert.h>
+#include <errno.h>
+#include <stdint.h> // for SIZE_MAX
 #include <stdio.h>
 #include <string.h>
 
@@ -300,3 +302,26 @@ duff_reallocator(void *ptr, size_t size) {
     g_reallocation_count--;
   return realloc(ptr, size);
 }
+
+// Portable remake of strndup(3) for C99; does not care about space efficiency
+char *
+portable_strndup(const char *s, size_t n) {
+  if ((s == NULL) || (n == SIZE_MAX)) {
+    errno = EINVAL;
+    return NULL;
+  }
+
+  char *const buffer = (char *)malloc(n + 1);
+  if (buffer == NULL) {
+    errno = ENOMEM;
+    return NULL;
+  }
+
+  errno = 0;
+
+  memcpy(buffer, s, n);
+
+  buffer[n] = '\0';
+
+  return buffer;
+}

expat/tests/common.h

@@ -146,6 +146,8 @@ extern void *duff_allocator(size_t size);
 
 extern void *duff_reallocator(void *ptr, size_t size);
 
+extern char *portable_strndup(const char *s, size_t n);
+
 #endif /* XML_COMMON_H */
 
 #ifdef __cplusplus