[lsan] Add debug option to "deflake" leaks

[vitalybuka]

There are hard to debug leaks which look like
false.

In general, repeating leak checking should not
affect set of leaks significantly, especial
at_exit leak checking.

But if we see significant discrepancy, it may give
us a clue for investigation.

[llvmbot]

@llvm/pr-subscribers-compiler-rt-sanitizer

Author: Vitaly Buka (vitalybuka)

Changes

There are hard to debug leaks which look like
false.

In general, repeating leak checking should not
affect set of leaks significantly, especial
at_exit leak checking.

But if we see significant discrepancy, it may give
us a clue for investigation.

---

Full diff: https://github.com/llvm/llvm-project/pull/112037.diff

3 Files Affected:

• (modified) compiler-rt/lib/lsan/lsan_common.cpp (+8-1)
• (modified) compiler-rt/lib/lsan/lsan_flags.inc (+1)
• (added) compiler-rt/test/lsan/TestCases/flag_retries.c (+23)

diff --git a/compiler-rt/lib/lsan/lsan_common.cpp b/compiler-rt/lib/lsan/lsan_common.cpp
index b584d1e9723fc8..8ed2cfc63cbae9 100644
--- a/compiler-rt/lib/lsan/lsan_common.cpp
+++ b/compiler-rt/lib/lsan/lsan_common.cpp
@@ -779,7 +779,7 @@ static bool PrintResults(LeakReport &report) {
   return unsuppressed_count;
 }
 
-static bool CheckForLeaks() {
+static bool CheckForLeaksOnce() {
   if (&__lsan_is_turned_off && __lsan_is_turned_off()) {
     VReport(1, "LeakSanitizer is disabled\n");
     return false;
@@ -831,6 +831,13 @@ static bool CheckForLeaks() {
   }
 }
 
+static bool CheckForLeaks() {
+  int with_leaks = 0;
+  for (int i = 0; i < flags()->retries; ++i)
+    with_leaks += CheckForLeaksOnce();
+  return with_leaks == flags()->retries;
+}
+
 static bool has_reported_leaks = false;
 bool HasReportedLeaks() { return has_reported_leaks; }
 
diff --git a/compiler-rt/lib/lsan/lsan_flags.inc b/compiler-rt/lib/lsan/lsan_flags.inc
index b7f28223b8189b..59edc0baa77d85 100644
--- a/compiler-rt/lib/lsan/lsan_flags.inc
+++ b/compiler-rt/lib/lsan/lsan_flags.inc
@@ -43,6 +43,7 @@ LSAN_FLAG(bool, use_poisoned, false,
           "Consider pointers found in poisoned memory to be valid.")
 LSAN_FLAG(bool, log_pointers, false, "Debug logging")
 LSAN_FLAG(bool, log_threads, false, "Debug logging")
+LSAN_FLAG(int, retries, 1, "Debug option to repeat leak checking multiple times")
 LSAN_FLAG(const char *, suppressions, "", "Suppressions file name.")
 LSAN_FLAG(int, thread_suspend_fail, 1,
           "Behaviour if thread suspendion all thread (0 - "
diff --git a/compiler-rt/test/lsan/TestCases/flag_retries.c b/compiler-rt/test/lsan/TestCases/flag_retries.c
new file mode 100644
index 00000000000000..3891a47bb0a566
--- /dev/null
+++ b/compiler-rt/test/lsan/TestCases/flag_retries.c
@@ -0,0 +1,23 @@
+// Test retries option of lsan.
+// RUN: %clang_lsan %s -o %t
+// RUN: %env_lsan_opts=use_stacks=0:use_registers=0:symbolize=0 %run %t foo 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK1
+// RUN: %env_lsan_opts=use_stacks=0:use_registers=0:symbolize=0:retries=12 %run %t 2>&1 | FileCheck %s --check-prefixes=CHECK,CHECK12
+
+#include <assert.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sanitizer/lsan_interface.h>
+
+void *p;
+
+int main(int argc, char *argv[]) {
+  fprintf(stderr, "Test alloc: %p.\n", malloc(1337));
+// CHECK: Test alloc:
+
+  assert(__lsan_do_recoverable_leak_check() == 1);
+// CHECK1-COUNT-1: SUMMARY: {{.*}}Sanitizer: 1337 byte
+// CHECK12-COUNT-12: SUMMARY: {{.*}}Sanitizer: 1337 byte
+
+  _exit(0);
+}

[github-actions]

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