Fix ASan stack range registration for main task

src/bthread/bthread.cpp

@@ -396,13 +396,6 @@ int bthread_equal(bthread_t t1, bthread_t t2) {
     return t1 == t2;
 }
 
-#ifdef BUTIL_USE_ASAN
-// Fixme!!!
-// The noreturn `bthread_exit' may cause a warning of ASan, but does not abort the program.
-//
-// ==94463==WARNING: ASan is ignoring requested __asan_handle_no_return: stack type: default top: 0x00016dd7f000; bottom 0x00010b1a4000; size: 0x000062bdb000 (1656598528)
-// False positive error reports may follow
-#endif // BUTIL_USE_ASAN
 void bthread_exit(void* retval) {
     bthread::TaskGroup* g = bthread::tls_task_group;
     if (g != NULL && !g->is_current_main_task()) {

src/bthread/task_group.cpp

@@ -247,6 +247,12 @@ TaskGroup::~TaskGroup() {
 }
 
 #ifdef BUTIL_USE_ASAN
+// Returns the **highest** address of the calling pthread's stack and its
+// total size, matching brpc's `StackStorage::bottom` convention (see comment
+// in bthread/stack.h: "Assume stack grows upwards"). Note that on Linux
+// `pthread_attr_getstack(3)` returns the lowest address of the region, so
+// we have to translate it; on macOS `pthread_get_stackaddr_np(3)` already
+// returns the stack base (highest address), so we use it as-is.
 int PthreadAttrGetStack(void*& stack_addr, size_t& stack_size) {
 #if defined(OS_MACOSX)
     stack_addr = pthread_get_stackaddr_np(pthread_self());
@@ -259,9 +265,13 @@ int PthreadAttrGetStack(void*& stack_addr, size_t& stack_size) {
         LOG(ERROR) << "Fail to get pthread attributes: " << berror(rc);
         return rc;
     }
-    rc = pthread_attr_getstack(&attr, &stack_addr, &stack_size);
+    void* stack_lowest = NULL;
+    rc = pthread_attr_getstack(&attr, &stack_lowest, &stack_size);
     if (0 != rc) {
         LOG(ERROR) << "Fail to get pthread stack: " << berror(rc);
+    } else {
+        // Translate lowest -> highest to match StackStorage::bottom.
+        stack_addr = (char*)stack_lowest + stack_size;
     }
     pthread_attr_destroy(&attr);
     return rc;