[compiler-rt] [ASan][Windows] Honor asan config flags on windows when set through the user function (PR #122990)

[Vitaly Buka via llvm-commits]

================
@@ -390,17 +390,57 @@ void PrintAddressSpaceLayout() {
           kHighShadowBeg > kMidMemEnd);
 }
 
+// Apply most options specified either through the ASAN_OPTIONS
+// environment variable, or through the `__asan_default_options` user function.
+//
+// This function may be called multiple times, once per weak reference callback
+// on Windows, so it needs to be idempotent.
+//
+// Context:
+// For maximum compatibility on Windows, it is necessary for ASan options to be
+// configured/registered/applied inside this method (instead of in
+// ASanInitInternal, for example). That's because, on Windows, the user-provided
+// definition for `__asan_default_opts` may not be bound when `ASanInitInternal`
+// is invoked (it is bound later).
+//
+// To work around the late binding on windows, `ApplyOptions` will be called,
+// again, after binding to the user-provided `__asan_default_opts` function.
+// Therefore, any flags not configured here are not guaranteed to be
+// configurable through `__asan_default_opts` on Windows.
+//
+//
+// For more details on this issue, see:
+// https://github.com/llvm/llvm-project/issues/117925
+void ApplyFlags() {
+  SetCanPoisonMemory(flags()->poison_heap);
+  SetMallocContextSize(common_flags()->malloc_context_size);
+
+  __sanitizer_set_report_path(common_flags()->log_path);
+
+  __asan_option_detect_stack_use_after_return =
+      flags()->detect_stack_use_after_return;
+
+  AllocatorOptions allocator_options;
+  allocator_options.SetFrom(flags(), common_flags());
+  ApplyAllocatorOptions(allocator_options);
+}
+
 static bool AsanInitInternal() {
   if (LIKELY(AsanInited()))
     return true;
   SanitizerToolName = "AddressSanitizer";
 
   CacheBinaryName();
 
-  // Initialize flags. This must be done early, because most of the
-  // initialization steps look at flags().
+  // Initialize flags and register weak function callbacks for windows.
+  // This must be done early, because most of the initialization steps look at
+  // flags().
   InitializeFlags();
 
+  // NOTE: The sleep before/after init` flags will not work on Windows when set
----------------
vitalybuka wrote:

This comment does not belong here, maybe to WaitForDebugger.
But it's irrelevant to the PR anyway

https://github.com/llvm/llvm-project/pull/122990