[memprof] Add flag to control profile dump at exit (#119452)

Add the `dump_at_exit` flag to control whether or not profiles should be
dumped when the program exits. Since we can call
`__memprof_profile_dump()` directly, we don't necessarily need to dump
profiles at exit.

compiler-rt/lib/memprof/memprof_allocator.cpp

@@ -301,7 +301,8 @@ struct Allocator {
 
   ~Allocator() {
     atomic_store_relaxed(&destructing, 1);
-    FinishAndWrite();
+    if (flags()->dump_at_exit)
+      FinishAndWrite();
   }
 
   static void PrintCallback(const uptr Key, LockedMemInfoBlock *const &Value,

compiler-rt/lib/memprof/memprof_flags.inc

@@ -38,4 +38,7 @@ MEMPROF_FLAG(bool, allocator_frees_and_returns_null_on_realloc_zero, true,
 MEMPROF_FLAG(bool, print_text, false,
   "If set, prints the heap profile in text format. Else use the raw binary serialization format.")
 MEMPROF_FLAG(bool, print_terse, false,
-             "If set, prints memory profile in a terse format. Only applicable if print_text = true.")
+             "If set, prints memory profile in a terse format. Only applicable "
+             "if print_text = true.")
+MEMPROF_FLAG(bool, dump_at_exit, true,
+             "If set, dump profiles when the program terminates.")

compiler-rt/test/memprof/TestCases/dump_at_exit.cpp

@@ -0,0 +1,16 @@
+// RUN: %clangxx_memprof %s -o %t
+
+// RUN: %env_memprof_opts=print_text=true:log_path=stdout:dump_at_exit=false %run %t | count 0
+// RUN: %env_memprof_opts=print_text=true:log_path=stdout:dump_at_exit=true %run %t | FileCheck %s
+
+#include <stdlib.h>
+#include <string.h>
+
+int main() {
+  char *x = (char *)malloc(10);
+  memset(x, 0, 10);
+  free(x);
+  return 0;
+}
+
+// CHECK: Recorded MIBs