[asan] Remove use_odr_indicator runtime flag

[vitalybuka]

Summary

Flag was added for testing 3 years ago. Probably it's time
to simplify code and usage by removing it.

[eugenis]

LGTM

lib/asan/asan_flags.inc

 ASAN_FLAG(int, detect_odr_violation, 2,
           "If >=2, detect violation of One-Definition-Rule (ODR); "
           "If ==1, detect ODR-violation only if the two variables "
           "have different sizes")
 ASAN_FLAG(const char *, suppressions, "", "Suppressions file name.")
 ASAN_FLAG(bool, halt_on_error, true,
           "Crash the program after printing the first error report "
           "(WARNING: USE AT YOUR OWN RISK!)")
-ASAN_FLAG(bool, use_odr_indicator, false,
-          "Use special ODR indicator symbol for ODR violation detection")
 ASAN_FLAG(bool, allocator_frees_and_returns_null_on_realloc_zero, true,
           "realloc(p, 0) is equivalent to free(p) by default (Same as the "
           "POSIX standard). If set to false, realloc(p, 0) will return a "
           "pointer to an allocated space which can not be used.")
 ASAN_FLAG(bool, verify_asan_link_order, true,
           "Check position of ASan runtime in library list (needs to be disabled"
           " when other library has to be preloaded system-wide)")

lib/asan/asan_globals.cc

 //   1) Non-zero value. In this case, odr_indicator is an address of
 //      corresponding indicator variable for given global.
 //   2) Zero. This means that we don't use private aliases for global variables
 //      and can freely check ODR violation with the first method.
 //
 // This routine chooses between two different methods of ODR violation
 // detection.
 static inline bool UseODRIndicator(const Global *g) {
-  // Use ODR indicator method iff use_odr_indicator flag is set and
-  // indicator symbol address is not 0.
-  return flags()->use_odr_indicator && g->odr_indicator > 0;
+  return g->odr_indicator > 0;
 }
 
 // Register a global variable.
 // This function may be called more than once for every global
 // so we store the globals in a map.
 static void RegisterGlobal(const Global *g) {
   CHECK(asan_inited);
   if (flags()->report_globals >= 2)

test/asan/TestCases/Darwin/odr-lto.cc

-// Check that -asan-use-private-alias and use_odr_indicator=1 silence the false
+// Check that -asan-use-private-alias silence the false
 // positive ODR violation on Darwin with LTO.
 
 // REQUIRES: lto
 
 // RUN: %clangxx_asan -DPART=0 -c %s -o %t-1.o -flto -mllvm -asan-use-private-alias
 // RUN: %clangxx_asan -DPART=1 -c %s -o %t-2.o -flto -mllvm -asan-use-private-alias
 // RUN: %clangxx_asan %t-1.o %t-2.o -o %t -flto
-// RUN: %env_asan_opts=use_odr_indicator=1 %run %t 2>&1 | FileCheck %s
+// RUN: %run %t 2>&1 | FileCheck %s
 
 #include <stdio.h>
 #include <stdlib.h>
 void putstest();
 
 #if PART == 1
 
 static const char *my_global = "test\n\00abc";

test/asan/TestCases/Linux/local_alias.cc

 // Test that mixing instrumented and non-instrumented code doesn't lead to crash.
 // Build two modules (one is instrumented, another is not) that have globals
 // with same names. Check, that ASan doesn't crash with CHECK failure or
 // false positive global-buffer-overflow due to sanitized library poisons
 // globals from non-sanitized one.
 //
 // FIXME: https://github.com/google/sanitizers/issues/316
 // XFAIL: android
 //
 // RUN: %clangxx_asan -DBUILD_INSTRUMENTED_DSO=1 -fPIC -shared -mllvm -asan-use-private-alias %s -o %t-INSTRUMENTED-SO.so
 // RUN: %clangxx -DBUILD_UNINSTRUMENTED_DSO=1 -fPIC -shared %s -o %t-UNINSTRUMENTED-SO.so
 // RUN: %clangxx %s -c -mllvm -asan-use-private-alias -o %t.o
 // RUN: %clangxx_asan %t.o %t-UNINSTRUMENTED-SO.so %t-INSTRUMENTED-SO.so -o %t-EXE
-// RUN: %env_asan_opts=use_odr_indicator=true %run %t-EXE
+// RUN: %run %t-EXE
 
 #if defined (BUILD_INSTRUMENTED_DSO)
 long h = 15;
 long f = 4;
 long foo(long *p) {
   return *p;
 }
 #elif defined (BUILD_UNINSTRUMENTED_DSO)

test/asan/TestCases/Linux/odr-violation.cc

 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=2:suppressions=%t.supp  not %run %t-ODR-EXE 2>&1 | FileCheck %s
 // RUN: echo "odr_violation:foo::G" > %t.supp
 // RUN: %env_asan_opts=fast_unwind_on_malloc=0:detect_odr_violation=2:suppressions=%t.supp      %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
 // RUN: rm -f %t.supp
 //
 // Use private aliases for global variables: use indicator symbol to detect ODR violation.
 // RUN: %clangxx_asan -DBUILD_SO=1 -fPIC -shared -mllvm -asan-use-private-alias %s -o %t-ODR-SO.so -DSZ=100
 // RUN: %clangxx_asan -mllvm -asan-use-private-alias %s %t-ODR-SO.so -Wl,-R. -o %t-ODR-EXE
-// RUN: %env_asan_opts=fast_unwind_on_malloc=0                              %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
-// RUN: %env_asan_opts=fast_unwind_on_malloc=0:use_odr_indicator=false      %run %t-ODR-EXE 2>&1 | FileCheck %s --check-prefix=DISABLED
-// RUN: %env_asan_opts=fast_unwind_on_malloc=0:use_odr_indicator=true   not %run %t-ODR-EXE 2>&1 | FileCheck %s
+// RUN: %env_asan_opts=fast_unwind_on_malloc=0 not %run %t-ODR-EXE 2>&1 | FileCheck %s
 
 // GNU driver doesn't handle .so files properly.
 // REQUIRES: Clang
 
 #ifndef SZ
 # define SZ 4
 #endif