portability: add reallocarray

portability/meson.build

@@ -9,6 +9,7 @@ check_functions = [
 	['mknodat', 'mknodat.c', 'NEED_MKNODAT', 'sys/stat.h'],
 	['pipe2', 'pipe2.c', 'NEED_PIPE2', 'unistd.h'],
 	['qsort_r', 'qsort_r.c', 'NEED_QSORT_R', 'stdlib.h'],
+	['reallocarray', 'reallocarray.c', 'NEED_REALLOCARRAY', 'stdlib.h'],
 	['strchrnul', 'strchrnul.c', 'NEED_STRCHRNUL', 'string.h'],
 	['strlcpy', 'strlcpy.c', 'NEED_STRLCPY', 'string.h'],
 ]

portability/reallocarray.c

+#include <errno.h>
+#include <stdlib.h>
+
+void *reallocarray(void *ptr, size_t m, size_t n)
+{
+	if (n && m > -1 / n) {
+		errno = ENOMEM;
+		return 0;
+	}
+	return realloc(ptr, m * n);
+}

portability/stdlib.h

 #pragma once
 #include_next <stdlib.h>
 
+#ifdef NEED_REALLOCARRAY
+void *reallocarray(void *ptr, size_t m, size_t n);
+#endif
+
 #ifdef NEED_QSORT_R
 void qsort_r(void *base, size_t nmemb, size_t size,
 	int (*compar)(const void *, const void *, void *),