From 2ff8c23edfbc7934bf7f94cc4972258f460a5169 Mon Sep 17 00:00:00 2001
From: "Enzo Persillet (Tutez)" <enzopersillet@gmail.com>
Date: Wed, 6 May 2026 21:03:57 +0200
Subject: [PATCH] Fix Immix working memory overflow with big blocks

Use GetWorkingMemory() instead of recomputing the Immix block size through
an int expression. With HXCPP_GC_BIG_BLOCKS, shifting the block count through
an int overflows once regular heap usage reaches roughly 2 GiB, which can
cause premature memory exhaustion or extremely long GC stalls.

Also store GC memory tuning thresholds as size_t and parse their environment
variables with strtoull so large values are not truncated.
---
 include/hx/GC.h        |  4 ++--
 src/hx/gc/GcCommon.cpp | 12 ++++++------
 src/hx/gc/Immix.cpp    |  6 +++---
 3 files changed, 11 insertions(+), 11 deletions(-)

diff --git a/include/hx/GC.h b/include/hx/GC.h
index 39480c2a6..a69523c97 100644
--- a/include/hx/GC.h
+++ b/include/hx/GC.h
@@ -158,10 +158,10 @@ extern int gPauseForCollect;
 
 
 // Minimum total memory - used + buffer for new objects
-extern int sgMinimumWorkingMemory;
+extern size_t sgMinimumWorkingMemory;
 
 // Minimum free memory - not counting used memory
-extern int sgMinimumFreeSpace;
+extern size_t sgMinimumFreeSpace;
 
 // Also ensure that the free memory is larger than this amount of used memory
 extern int sgTargetFreeSpacePercentage;
diff --git a/src/hx/gc/GcCommon.cpp b/src/hx/gc/GcCommon.cpp
index f336fd615..fdc93341a 100644
--- a/src/hx/gc/GcCommon.cpp
+++ b/src/hx/gc/GcCommon.cpp
@@ -27,11 +27,11 @@ extern void __hxt_new_string(void* result, int size);
 namespace hx
 {
 #if defined(HX_MACOS) || defined(HX_WINDOWS) || defined(HX_LINUX) || defined(__ORBIS__)
-int sgMinimumWorkingMemory       = 20*1024*1024;
-int sgMinimumFreeSpace           = 10*1024*1024;
+size_t sgMinimumWorkingMemory       = 20*1024*1024;
+size_t sgMinimumFreeSpace           = 10*1024*1024;
 #else
-int sgMinimumWorkingMemory       = 8*1024*1024;
-int sgMinimumFreeSpace           = 4*1024*1024;
+size_t sgMinimumWorkingMemory       = 8*1024*1024;
+size_t sgMinimumFreeSpace           = 4*1024*1024;
 #endif
 // Once you use more than the minimum, this kicks in...
 int sgTargetFreeSpacePercentage  = 100;
@@ -48,7 +48,7 @@ void CommonInitAlloc()
    const char *minimumWorking = getenv("HXCPP_MINIMUM_WORKING_MEMORY");
    if (minimumWorking)
    {
-      int mem =  atoi(minimumWorking);
+      size_t mem = strtoull(minimumWorking, 0, 10);
       if (mem>0)
          sgMinimumWorkingMemory = mem;
    }
@@ -56,7 +56,7 @@ void CommonInitAlloc()
    const char *minimumFreeSpace = getenv("HXCPP_MINIMUM_FREE_SPACE");
    if (minimumFreeSpace)
    {
-      int mem =  atoi(minimumFreeSpace);
+      size_t mem = strtoull(minimumFreeSpace, 0, 10);
       if (mem>0)
          sgMinimumFreeSpace = mem;
    }
diff --git a/src/hx/gc/Immix.cpp b/src/hx/gc/Immix.cpp
index 74672a54a..a434adc21 100644
--- a/src/hx/gc/Immix.cpp
+++ b/src/hx/gc/Immix.cpp
@@ -3543,11 +3543,11 @@ class GlobalAllocator
       #if defined(SHOW_MEM_EVENTS_VERBOSE) || defined(SHOW_FRAGMENTATION_BLOCKS)
       if (inJustBorrowing)
       {
-         GCLOG("Borrow Blocks %d = %d k\n", mAllBlocks.size(), (mAllBlocks.size() << IMMIX_BLOCK_BITS)>>10);
+         GCLOG("Borrow Blocks %d = %d k\n", mAllBlocks.size(), (int)(GetWorkingMemory() >> 10));
       }
       else
       {
-         GCLOG("Blocks %d = %d k\n", mAllBlocks.size(), (mAllBlocks.size() << IMMIX_BLOCK_BITS)>>10);
+         GCLOG("Blocks %d = %d k\n", mAllBlocks.size(), (int)(GetWorkingMemory() >> 10));
       }
       #endif
 
@@ -5235,7 +5235,7 @@ class GlobalAllocator
       #endif
 
       // Large alloc target
-      int blockSize =  mAllBlocks.size()<<IMMIX_BLOCK_BITS;
+      size_t blockSize =  GetWorkingMemory();
       if (blockSize > mLargeAllocSpace)
          mLargeAllocSpace = blockSize;
       mLargeAllocForceRefresh = mLargeAllocated + mLargeAllocSpace;