wasm2c: Add optional WASM_RT_GROW_FAILED_HANDLER to be notified of memory growth failures

2 files changed, 22 insertions, 2 deletions

diff --git a/wasm2c/README.md b/wasm2c/README.md
index 26dfb368..625ce25b 100644
--- a/wasm2c/README.md
+++ b/wasm2c/README.md
@@ -322,7 +322,13 @@ an i32 or i64 address.
 of pages. If there isn't enough memory to do so, or the new page count would be
 greater than the maximum page count, the function must fail by returning
 `0xffffffff`. If the function succeeds, it must return the previous size of the
-memory instance, in pages.
+memory instance, in pages. The host can optionally be notified of failures by
+defining a function the signature `void wasm2c_grow_failed_handler()` and
+compiling the runtime with the with macro definition `#define
+WASM_RT_GROW_FAILED_HANDLER wasm2c_grow_failed_handler`. It is recommended that
+you add this macro definition via a compiler flag
+(`-WASM_RT_GROW_FAILED_HANDLER=wasm2c_grow_failed_handler` on clang/gcc).
+
 
 `wasm_rt_free_memory` frees the memory instance.
 
diff --git a/wasm2c/wasm-rt-impl.c b/wasm2c/wasm-rt-impl.c
index 8e4823f0..25532e95 100644
--- a/wasm2c/wasm-rt-impl.c
+++ b/wasm2c/wasm-rt-impl.c
@@ -70,6 +70,10 @@ static WASM_RT_THREAD_LOCAL wasm_rt_jmp_buf* g_unwind_target;
 extern void WASM_RT_TRAP_HANDLER(wasm_rt_trap_t code);
 #endif
 
+#ifdef WASM_RT_GROW_FAILED_HANDLER
+extern void WASM_RT_GROW_FAILED_HANDLER();
+#endif
+
 void wasm_rt_trap(wasm_rt_trap_t code) {
   assert(code != WASM_RT_TRAP_NONE);
 #if WASM_RT_USE_STACK_DEPTH_COUNT
@@ -345,7 +349,7 @@ void wasm_rt_allocate_memory(wasm_rt_memory_t* memory,
 #endif
 }
 
-uint64_t wasm_rt_grow_memory(wasm_rt_memory_t* memory, uint64_t delta) {
+static uint64_t grow_memory_impl(wasm_rt_memory_t* memory, uint64_t delta) {
   uint64_t old_pages = memory->pages;
   uint64_t new_pages = memory->pages + delta;
   if (new_pages == 0) {
@@ -382,6 +386,16 @@ uint64_t wasm_rt_grow_memory(wasm_rt_memory_t* memory, uint64_t delta) {
   return old_pages;
 }
 
+uint64_t wasm_rt_grow_memory(wasm_rt_memory_t* memory, uint64_t delta) {
+  uint64_t ret = grow_memory_impl(memory, delta);
+#ifdef WASM_RT_GROW_FAILED_HANDLER
+  if (ret == -1) {
+    WASM_RT_GROW_FAILED_HANDLER();
+  }
+#endif
+  return ret;
+}
+
 void wasm_rt_free_memory(wasm_rt_memory_t* memory) {
 #if WASM_RT_USE_MMAP
   const uint64_t mmap_size = get_allocation_size_for_mmap(memory);