From cd99f1b6431539f56158cb90e102be7ab9518ed5 Mon Sep 17 00:00:00 2001
From: Romain Vimont <rom@rom1v.com>
Date: Tue, 28 Feb 2023 21:43:19 +0100
Subject: [PATCH] Add compat for reallocarray()

This function fails safely in the case where the multiplication would
overflow.
---
 app/meson.build  |  1 +
 app/src/compat.c | 15 ++++++++++++++-
 app/src/compat.h |  4 ++++
 3 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/app/meson.build b/app/meson.build
index 85ded6ef..acb238cf 100644
--- a/app/meson.build
+++ b/app/meson.build
@@ -173,6 +173,7 @@ check_functions = [
     'vasprintf',
     'nrand48',
     'jrand48',
+    'reallocarray',
 ]
 
 foreach f : check_functions
diff --git a/app/src/compat.c b/app/src/compat.c
index bb0152aa..785f843c 100644
--- a/app/src/compat.c
+++ b/app/src/compat.c
@@ -3,6 +3,9 @@
 #include "config.h"
 
 #include <assert.h>
+#ifndef HAVE_REALLOCARRAY
+# include <errno.h>
+#endif
 #include <stdlib.h>
 #include <stdio.h>
 #include <stdarg.h>
@@ -93,5 +96,15 @@ long jrand48(unsigned short xsubi[3]) {
     return v.i;
 }
 #endif
-
+#endif
+
+#ifndef HAVE_REALLOCARRAY
+void *reallocarray(void *ptr, size_t nmemb, size_t size) {
+    size_t bytes;
+    if (__builtin_mul_overflow(nmemb, size, &bytes)) {
+      errno = ENOMEM;
+      return NULL;
+    }
+    return realloc(ptr, bytes);
+}
 #endif
diff --git a/app/src/compat.h b/app/src/compat.h
index c720ddfe..22563421 100644
--- a/app/src/compat.h
+++ b/app/src/compat.h
@@ -74,4 +74,8 @@ long nrand48(unsigned short xsubi[3]);
 long jrand48(unsigned short xsubi[3]);
 #endif
 
+#ifndef HAVE_REALLOCARRAY
+void *reallocarray(void *ptr, size_t nmemb, size_t size);
+#endif
+
 #endif