From a092599a1af26e657bb93d4e8757aea8c6e0964b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Nils=20O=2E=20Sel=C3=A5sdal?= <nos@utel.tech>
Date: Tue, 9 Jun 2026 10:41:51 +0200
Subject: [PATCH] Some comments

---
 src/arena.c    |  1 +
 src/arena.h    | 16 +++++++---------
 src/main.c     | 14 ++++++++++----
 src/platform.c | 10 +++++-----
 4 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/src/arena.c b/src/arena.c
index 59d2e77..aac70a2 100644
--- a/src/arena.c
+++ b/src/arena.c
@@ -109,6 +109,7 @@ void arena_pop_to(Arena *arena, U32 abs_pos)
         } else {
             U32 new_pos = abs_pos - block->base_pos;
             new_pos = Max(MemoryBlock_Header_Size, new_pos);
+            // Disallow arbirary pops to positions that previously were not commited.
             Assert(new_pos <= block->committed_pos);
             block->pos = new_pos;
             ASAN_POISON_MEMORY_REGION(&block->base[block->pos], memoryblock_available(block));
diff --git a/src/arena.h b/src/arena.h
index cdbf6ab..9e9e971 100644
--- a/src/arena.h
+++ b/src/arena.h
@@ -14,18 +14,19 @@ struct ArenaParams {
 typedef struct MemoryBlock MemoryBlock;
 struct MemoryBlock {
     U8 *base;
-    U32 size;
-    U32 pos;          // start of next allocation
-    U32 base_pos;     // absolute position of base relative to the first linked arena
-    U32 committed_pos;
+    U32 size;           // Block size, page aligned
+    U32 pos;            // start of next allocation
+    U32 base_pos;       // absolute position of base relative to the first linked arena
+    U32 committed_pos;  // end of committed region. Will be page aligned
     MemoryBlock *prev;
 };
 
 typedef struct Arena Arena;
 struct Arena {
     MemoryBlock *current;
-    U32 block_size;
-    U32 commit_size;
+    U32 block_size;     // requested block size
+    U32 commit_size;    // requested commit size
+    U32 page_size;      // cached page size
     ArenaFlags flags;
     S32 checkpoint_level;
 };
@@ -39,10 +40,7 @@ struct ArenaCheckPoint {
 StaticAssert(sizeof(MemoryBlock) <= 64);
 #define MemoryBlock_Header_Size 64u
 
-
-
 void arena_init(Arena *arena, const ArenaParams *params);
-
 void arena_free(Arena *arena);
 void *arena_push(Arena *arena, U32 size, U32 align);
 
diff --git a/src/main.c b/src/main.c
index 41de530..dfdbb9d 100644
--- a/src/main.c
+++ b/src/main.c
@@ -21,6 +21,7 @@ void arena_dump(const Arena *arena)
 }
 static void arena_test_1(void)
 {
+    TRACEF("\n");
     ArenaParams arena_params = {};
     U32 arena_size = MB(1) + MemoryBlock_Header_Size;
     U32 commit_size = KB(8);
@@ -47,6 +48,8 @@ static void arena_test_1(void)
 
 static void arena_test_2(void)
 {
+    TRACEF("\n");
+
     ArenaParams arena_params = {};
     U32 arena_size = MB(1) + MemoryBlock_Header_Size;
     U32 commit_size = KB(16);
@@ -89,15 +92,18 @@ static void arena_test_2(void)
     arena_pop_to(&arena, 1089);
     arena_dump(&arena);
     arena_pop_to(&arena, 0);
-
+    ptr = arena_push(&arena, MB(1), 8);
+    MemoryZero(ptr, MB(1));
     arena_free(&arena);
 }
 
 static void arena_test_3(void)
 {
+    TRACEF("\n");
+
     ArenaParams arena_params = {};
     U32 arena_size = KB(97) + MemoryBlock_Header_Size;
-    U32 commit_size = KB(32);
+    U32 commit_size = KB(97);
     arena_params.size = arena_size;
     arena_params.commit_size = commit_size;
     Arena arena;
@@ -116,7 +122,7 @@ static void arena_test_3(void)
 
 int main(int argc, char *argv[])
 {
-    //arena_test_1();
-    //arena_test_2();
+    arena_test_1();
+    arena_test_2();
     arena_test_3();
 }
diff --git a/src/platform.c b/src/platform.c
index f8198db..654fe05 100644
--- a/src/platform.c
+++ b/src/platform.c
@@ -30,7 +30,7 @@ void *memory_allocate(size_t size)
     Assert(IsPow2(size));
 
     void *mem = mmap(0, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS  | MAP_PRIVATE, -1, 0);
-    TRACEF("memory_allocate size=%zu mem=%p\n", size, mem);
+    TRACEF("memory_allocate size=%7zu mem=%p\n", size, mem);
     if (mem == MAP_FAILED) {
         mem = NULL;
     }
@@ -39,7 +39,7 @@ void *memory_allocate(size_t size)
 
 void memory_free(void *mem, size_t size)
 {
-    TRACEF("        memory_free     size=%zu mem=%p\n", size, mem);
+    TRACEF("        memory_free     size=%7zu mem=%p\n", size, mem);
     Assert(IsPageAligned((uintptr_t)mem));
     Assert(IsPageAligned(size));
     int rc = munmap(mem, size);
@@ -51,7 +51,7 @@ void *memory_reserve(size_t size)
 {
     Assert(IsPageAligned(size));
     void *mem = mmap(0, size, PROT_NONE, MAP_ANONYMOUS  | MAP_PRIVATE, -1, 0);
-    TRACEF("memory_reserve  size=%zu mem=%p\n", size, mem);
+    TRACEF("memory_reserve  size=%7zu mem=%p\n", size, mem);
     if (mem == MAP_FAILED) {
         mem = NULL;
     }
@@ -62,7 +62,7 @@ void memory_commit(void *mem, size_t size)
 {
     Assert(IsPageAligned((uintptr_t)mem));
     Assert(IsPageAligned(size));
-    TRACEF("memory_commit   size=%zu mem=%p\n", size, mem);
+    TRACEF("memory_commit   size=%7zu mem=%p\n", size, mem);
 
     int rc;
     rc = mprotect(mem, size, PROT_READ | PROT_WRITE);
@@ -73,7 +73,7 @@ void memory_commit(void *mem, size_t size)
 
 void memory_decommit(void *mem, size_t size)
 {
-    TRACEF("memory_decommit size=%zu mem=%p\n", size, mem);
+    TRACEF("memory_decommit size=%7zu mem=%p\n", size, mem);
     Assert(IsPageAligned((uintptr_t)mem));
     Assert(IsPageAligned(size));
     int rc;