Export of internal Abseil changes

--
4b566a7deeba5db473c83f4924c1d182a002779f by Abseil Team <absl-team@google.com>:

Add absl::LeakCheckerIsActive to check whether a leak checker is built into the
target and enabled. For LeakSanitizer, it is by default enabled unless
__lsan_is_turned_off() is defined and returns true.

PiperOrigin-RevId: 364654465

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0a56ff5310b66f9d1ff5e5e2a053335ecfb5c75b by Abseil Team <absl-team@google.com>:

Update absl::FromTM documentation to reflect implementation.

PiperOrigin-RevId: 364388743
GitOrigin-RevId: 4b566a7deeba5db473c83f4924c1d182a002779f
Change-Id: I8df35b761b532e79d620f484153083c3499ef55b

absl/debugging/BUILD.bazel

@@ -260,6 +260,7 @@ cc_library(
     visibility = ["//visibility:private"],
     deps = [
         "//absl/base:config",
+        "//absl/base:core_headers",
     ],
 )
 
@@ -273,6 +274,7 @@ cc_library(
     visibility = ["//visibility:private"],
     deps = [
         "//absl/base:config",
+        "//absl/base:core_headers",
     ],
 )
 

absl/debugging/leak_check.cc

@@ -16,6 +16,7 @@
 // When lsan is not linked in, these functions are not available,
 // therefore Abseil code which depends on these functions is conditioned on the
 // definition of LEAK_SANITIZER.
+#include "absl/base/attributes.h"
 #include "absl/debugging/leak_check.h"
 
 #ifndef LEAK_SANITIZER
@@ -23,6 +24,7 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 bool HaveLeakSanitizer() { return false; }
+bool LeakCheckerIsActive() { return false; }
 void DoIgnoreLeak(const void*) { }
 void RegisterLivePointers(const void*, size_t) { }
 void UnRegisterLivePointers(const void*, size_t) { }
@@ -35,9 +37,22 @@ ABSL_NAMESPACE_END
 
 #include <sanitizer/lsan_interface.h>
 
+#if ABSL_HAVE_ATTRIBUTE_WEAK
+extern "C" ABSL_ATTRIBUTE_WEAK int __lsan_is_turned_off();
+#endif
+
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 bool HaveLeakSanitizer() { return true; }
+
+#if ABSL_HAVE_ATTRIBUTE_WEAK
+bool LeakCheckerIsActive() {
+  return !(&__lsan_is_turned_off && __lsan_is_turned_off());
+}
+#else
+bool LeakCheckerIsActive() { return true; }
+#endif
+
 bool FindAndReportLeaks() { return __lsan_do_recoverable_leak_check(); }
 void DoIgnoreLeak(const void* ptr) { __lsan_ignore_object(ptr); }
 void RegisterLivePointers(const void* ptr, size_t size) {

absl/debugging/leak_check.h

@@ -43,6 +43,12 @@ ABSL_NAMESPACE_BEGIN
 // currently built into this target.
 bool HaveLeakSanitizer();
 
+// LeakCheckerIsActive()
+//
+// Returns true if a leak-checking sanitizer (either ASan or standalone LSan) is
+// currently built into this target and is turned on.
+bool LeakCheckerIsActive();
+
 // DoIgnoreLeak()
 //
 // Implements `IgnoreLeak()` below. This function should usually

absl/debugging/leak_check_test.cc

@@ -23,8 +23,10 @@ namespace {
 TEST(LeakCheckTest, DetectLeakSanitizer) {
 #ifdef ABSL_EXPECT_LEAK_SANITIZER
   EXPECT_TRUE(absl::HaveLeakSanitizer());
+  EXPECT_TRUE(absl::LeakCheckerIsActive());
 #else
   EXPECT_FALSE(absl::HaveLeakSanitizer());
+  EXPECT_FALSE(absl::LeakCheckerIsActive());
 #endif
 }
 

absl/time/time.h

@@ -1180,11 +1180,15 @@ inline Time FromDateTime(int64_t year, int mon, int day, int hour,
 //
 // Converts the `tm_year`, `tm_mon`, `tm_mday`, `tm_hour`, `tm_min`, and
 // `tm_sec` fields to an `absl::Time` using the given time zone. See ctime(3)
-// for a description of the expected values of the tm fields. If the indicated
-// time instant is not unique (see `absl::TimeZone::At(absl::CivilSecond)`
-// above), the `tm_isdst` field is consulted to select the desired instant
-// (`tm_isdst` > 0 means DST, `tm_isdst` == 0 means no DST, `tm_isdst` < 0
-// means use the post-transition offset).
+// for a description of the expected values of the tm fields. If the civil time
+// is unique (see `absl::TimeZone::At(absl::CivilSecond)` above), the matching
+// time instant is returned.  Otherwise, the `tm_isdst` field is consulted to
+// choose between the possible results.  For a repeated civil time, `tm_isdst !=
+// 0` returns the matching DST instant, while `tm_isdst == 0` returns the
+// matching non-DST instant.  For a skipped civil time there is no matching
+// instant, so `tm_isdst != 0` returns the DST instant, and `tm_isdst == 0`
+// returns the non-DST instant, that would have matched if the transition never
+// happened.
 Time FromTM(const struct tm& tm, TimeZone tz);
 
 // ToTM()