From 256de6841041067ab71c545fd3a2cd82d84a5313 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nils=20O=2E=20Sel=C3=A5sdal?= <nos@utel.tech>
Date: Sat, 6 Jun 2026 13:52:36 +0200
Subject: [PATCH] Integrate address sanitizer

---
 build.sh        |  2 +-
 src/arena.c     |  6 ++++++
 src/arena.h     | 13 +++++++++++++
 src/base_core.h |  7 ++++++-
 src/main.c      |  6 ++++--
 5 files changed, 30 insertions(+), 4 deletions(-)

diff --git a/build.sh b/build.sh
index 1483a3a..b4be581 100755
--- a/build.sh
+++ b/build.sh
@@ -1,3 +1,3 @@
 #!/bin/sh
 set -x
-gcc  -ggdb -Wall -Wextra -Wno-unused-parameter -Wno-unused-variable -std=gnu23 src/*c
+gcc  -fsanitize=address -ggdb -Wall -Wextra -Wno-unused-parameter -Wno-unused-variable -std=gnu23 $CFLAGS src/*c
diff --git a/src/arena.c b/src/arena.c
index 852b4dd..e05648e 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -26,6 +26,8 @@ Arena *arena_alloc_(const ArenaParams *params)
 
     // Note: only backend now is malloc
     void *base = memory_allocate(params->size);
+    //((U8*)base)[1023+ARENA_HEADER_SZ] = 1;
+
     Assert(base != NULL);
 
     Arena *arena = (Arena *)base;
@@ -37,6 +39,7 @@ Arena *arena_alloc_(const ArenaParams *params)
     arena->prev     = NULL;
     arena->checkpoint_level = 0;
 
+    ASAN_POISON_MEMORY_REGION(&arena->base[arena->pos], arena_available(arena));
     return arena;
 }
 
@@ -83,6 +86,7 @@ void *arena_push(Arena *arena, U32 size, U32 align)
     U8 *mem     = &current->base[start_pos];
     current->pos  = end_pos;
 
+    ASAN_UNPOISON_MEMORY_REGION(mem, size);
     return mem;
 }
 
@@ -94,6 +98,7 @@ void arena_pop_to(Arena *arena, U32 abs_pos)
         Arena *prev = current->prev;
 
         if (current->base_pos >= abs_pos) {
+            ASAN_UNPOISON_MEMORY_REGION(current->base, current->size);
             memory_release(current->base);
             arena->current = prev;
         } else {
@@ -102,6 +107,7 @@ void arena_pop_to(Arena *arena, U32 abs_pos)
             // is the right thing . shouldn't be able to pop to larger than what's already commited
             Assert(new_pos <= current->size);
             current->pos = new_pos;
+            ASAN_POISON_MEMORY_REGION(&current->base[current->pos], arena_available(arena));
             break;
         }
 
diff --git a/src/arena.h b/src/arena.h
index fb21cea..f493fd0 100644
--- a/src/arena.h
+++ b/src/arena.h
@@ -1,6 +1,19 @@
 #pragma once
 #include "base_core.h"
 
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+#include <sanitizer/asan_interface.h>
+#define ASAN_POISON_MEMORY_REGION(addr, size) \
+  __asan_poison_memory_region((addr), (size))
+#define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+  __asan_unpoison_memory_region((addr), (size))
+#else
+#define ASAN_POISON_MEMORY_REGION(addr, size) \
+  ((void)(addr), (void)(size))
+#define ASAN_UNPOISON_MEMORY_REGION(addr, size) \
+  ((void)(addr), (void)(size))
+#endif
+
 typedef U32 ArenaFlags;
 
 typedef struct ArenaParams ArenaParams;
diff --git a/src/base_core.h b/src/base_core.h
index 104665b..ae62c85 100644
--- a/src/base_core.h
+++ b/src/base_core.h
@@ -187,7 +187,12 @@ typedef unsigned __int128 U128;
 
 // memory
 #define MemSet(ptr, val, len)       memset(ptr, val, len)
-#define MemoryZero(ptr, len)        explicit_bzero(ptr,len)
+#if __has_feature(address_sanitizer) || defined(__SANITIZE_ADDRESS__)
+#define MemoryZero(ptr, len)        memset(ptr, 0, len)
+// explicity bzero is usually not being intercepted
+#else
+#define MemoryZero(ptr, len)        explicit_bzero(ptr, len)
+#endif
 #define MemMove(dst, src, len)      memmove(dst, src, len)
 #define MemCpy(dst, src, len)       memcpy(dst, src, len)
 #define MemAppend(dst, src, len)    mempcpy(dst, src, len)
diff --git a/src/main.c b/src/main.c
index 03e30d0..ae11172 100644
--- a/src/main.c
+++ b/src/main.c
@@ -24,8 +24,8 @@ static void arena_test_1(void)
     arena_params.size = 1024+ARENA_HEADER_SZ;
     Arena *arena = arena_alloc_(&arena_params);
     arena_dump(arena);
-    char *ptr = arena_push(arena, 1024, 1);
-    MemoryZero(ptr, 1024);
+    char *ptr = arena_push(arena, 512, 1);
+    MemoryZero(ptr, 512);
     printf("Allocated ptr %p\n", ptr);
     arena_dump(arena);
     ptr = arena_push(arena, 512, 1);
@@ -62,6 +62,7 @@ static void arena_test_2(void)
     arena_pop_to(arena, 1088);
     arena_dump(arena);
     ptr = arena_push(arena, 1, 1);
+    ((U8*)ptr)[1] =1; //OOB
     ptr = arena_push(arena, 1, 1);
     arena_pop_to(arena, 1089);
     arena_dump(arena);
@@ -71,5 +72,6 @@ static void arena_test_2(void)
 
 int main(int argc, char *argv[])
 {
+    arena_test_1();
     arena_test_2();
 }