From b0fc1912eab251175659cb18dcdcd40bd116f465 Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Wed, 22 Jul 2020 11:04:48 +0000
Subject: [PATCH] Create mimalloc heaps only when necessary.

The mimalloc temporary heap is a thread-local object that uses RAII
to manage heap lifetimes even in threads that are created implicitly,
e.g. by OpenMP. However, not all threads are necessarily created by
the application; graphics drivers may create their own threads, and
this can lead to deadlocks when combined with library unloading.

Fixes #657.
---
 src/platform/platform.cpp | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/src/platform/platform.cpp b/src/platform/platform.cpp
index 934220c..a080982 100644
--- a/src/platform/platform.cpp
+++ b/src/platform/platform.cpp
@@ -684,20 +684,21 @@ void DebugPrint(const char *fmt, ...) {
 //-----------------------------------------------------------------------------
 
 struct MimallocHeap {
-    mi_heap_t *heap = mi_heap_new();
-
-    MimallocHeap() {
-        ssassert(heap != NULL, "out of memory");
-    }
+    mi_heap_t *heap = NULL;
 
     ~MimallocHeap() {
-        mi_heap_destroy(heap);
+        if(heap != NULL)
+            mi_heap_destroy(heap);
     }
 };
 
 static thread_local MimallocHeap TempArena;
 
 void *AllocTemporary(size_t size) {
+    if(TempArena.heap == NULL) {
+        TempArena.heap = mi_heap_new();
+        ssassert(TempArena.heap != NULL, "out of memory");
+    }
     void *ptr = mi_heap_zalloc(TempArena.heap, size);
     ssassert(ptr != NULL, "out of memory");
     return ptr;