[TSan] Align default value of `detect_deadlocks` flag with actual behavior

[yln]

Summary

I tricked myself into thinking that deadlock detection is off by default in TSan by looking at the default value of the detect_deadlocks flag and outdated docs. (Created a pull request to update docs.)
I even managed to confuse others: https://groups.google.com/forum/#!topic/thread-sanitizer/xYvnAYwtoDk

However, the default value is overwritten in code (TSan_flags.cc:InitializeFlags). The TSan/deadlock tests also rely on this

This changes aligns the default value of the flag with the actual default behavior.

[dvyukov]

Thanks!
Merging this now.

[dvyukov]

Merged as 349609.

compiler-rt/lib/sanitizer_common/sanitizer_flags.inc

 COMMON_FLAG(HandleSignalMode, handle_sigfpe, kHandleSignalYes,
             COMMON_FLAG_HANDLE_SIGNAL_HELP(SIGFPE))
 #undef COMMON_FLAG_HANDLE_SIGNAL_HELP
 COMMON_FLAG(bool, allow_user_segv_handler, true,
             "Deprecated. True has no effect, use handle_sigbus=1. If false, "
             "handle_*=1 will be upgraded to handle_*=2.")
 COMMON_FLAG(bool, use_sigaltstack, true,
             "If set, uses alternate stack for signal handling.")
-COMMON_FLAG(bool, detect_deadlocks, false,
+COMMON_FLAG(bool, detect_deadlocks, true,
             "If set, deadlock detection is enabled.")
 COMMON_FLAG(
     uptr, clear_shadow_mmap_threshold, 64 * 1024,
     "Large shadow regions are zero-filled using mmap(NORESERVE) instead of "
     "memset(). This is the threshold size in bytes.")
 COMMON_FLAG(const char *, color, "auto",
             "Colorize reports: (always|never|auto).")
 COMMON_FLAG(

compiler-rt/lib/tsan/rtl/tsan_flags.cc

SetCommonFlagsDefaults();
     // Override some common flags defaults.
     CommonFlags cf;
     cf.CopyFrom(*common_flags());
     cf.allow_addr2line = true;
     if (SANITIZER_GO) {
       // Does not work as expected for Go: runtime handles SIGABRT and crashes.
       cf.abort_on_error = false;
       // Go does not have mutexes.
-    } else {
-      cf.detect_deadlocks = true;
+      cf.detect_deadlocks = false;
     }
     cf.print_suppressions = false;
     cf.stack_trace_format = "    #%n %f %S %M";
     cf.exitcode = 66;
     cf.intercept_tls_get_addr = true;
     OverrideCommonFlags(cf);
   }
 

compiler-rt/test/tsan/deadlock_detector_stress_test.cc

 // RUN: %clangxx_tsan %s -o %t -DLockType=PthreadMutex
-// RUN: %env_tsan_opts=detect_deadlocks=1 %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NOT-SECOND
-// RUN: %env_tsan_opts=detect_deadlocks=1:second_deadlock_stack=1 %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-SECOND
+// RUN: %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-NOT-SECOND
+// RUN: %env_tsan_opts=second_deadlock_stack=1 %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-SECOND
 // RUN: %clangxx_tsan %s -o %t -DLockType=PthreadSpinLock
-// RUN: %env_tsan_opts=detect_deadlocks=1 %deflake %run %t | FileCheck %s
+// RUN: %deflake %run %t | FileCheck %s
 // RUN: %clangxx_tsan %s -o %t -DLockType=PthreadRWLock
-// RUN: %env_tsan_opts=detect_deadlocks=1 %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-RD
+// RUN: %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-RD
 // RUN: %clangxx_tsan %s -o %t -DLockType=PthreadRecursiveMutex
-// RUN: %env_tsan_opts=detect_deadlocks=1 %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-REC
+// RUN: %deflake %run %t | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-REC
 #include "test.h"
 #undef NDEBUG
 #include <assert.h>
 #include <new>
 
 #ifndef LockType
 #define LockType PthreadMutex
 #endif

compiler-rt/test/tsan/mutex_cycle2.c

 // RUN: %clangxx_tsan %s -o %t
-// RUN:                                 not %run %t 2>&1 | FileCheck %s
+// RUN:                                   not %run %t 2>&1 | FileCheck %s
 // RUN: %env_tsan_opts=detect_deadlocks=1 not %run %t 2>&1 | FileCheck %s
 // RUN: %env_tsan_opts=detect_deadlocks=0     %run %t 2>&1 | FileCheck %s --check-prefix=DISABLED
 // RUN: echo "deadlock:main" > %t.supp
 // RUN: %env_tsan_opts=suppressions='%t.supp' %run %t 2>&1 | FileCheck %s --check-prefix=DISABLED
 // RUN: echo "deadlock:zzzz" > %t.supp
 // RUN: %env_tsan_opts=suppressions='%t.supp' not %run %t 2>&1 | FileCheck %s
 #include <pthread.h>
 #include <stdio.h>