Export of internal Abseil changes

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7f5caec21a1a88db6486b8bc2e5f6d5baba076ed by Derek Mauro <dmauro@google.com>:

Tag absl::StatusOr with [[nodiscard]] when it is available

[[nodiscard]] provides better diagnostics on classes than the current
ABSL_MUST_USE_RESULT, which expands to
__attribute__((warn_unused_result))

Ideally we would make ABSL_MUST_USE_RESULT expand to [[nodiscard]], but
we would need to fix all code to build with [[nodiscard]] first.

PiperOrigin-RevId: 422628161

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236be69f0f34ccaa3adc831075613847797e6557 by Jorg Brown <jorg@google.com>:

Make sure all of absl/strings compiles even with -Wsign-compare and -Wconversion warnings.

PiperOrigin-RevId: 422573904

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005669883a8794e6d19dc4bbb4f0e18032e2fbc9 by Chris Kennelly <ckennelly@google.com>:

Include sampling stride in hashtable sampling data.

This allows us to weight each sample to control for our sampling rate.

PiperOrigin-RevId: 421886935

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78046ce6b429b9f5b6c97b05e8448a791db93bbe by Abseil Team <absl-team@google.com>:

Use __builtin_bit_cast for absl::bit_cast when possible

This makes absl::bit_cast match the requirements of the standard when compiler support exists.

PiperOrigin-RevId: 421883999

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f397461f4bbeabd32437df0f2275663aeb51adb2 by Derek Mauro <dmauro@google.com>:

Tag absl::Status with [[nodiscard]] when it is available

[[nodiscard]] provides better diagnostics on classes than the current
ABSL_MUST_USE_RESULT, which expands to
__attribute__((warn_unused_result))

Ideally we would make ABSL_MUST_USE_RESULT expand to [[nodiscard]], but
we would need to fix all code to build with [[nodiscard]] first.

PiperOrigin-RevId: 421825565
GitOrigin-RevId: 7f5caec21a1a88db6486b8bc2e5f6d5baba076ed
Change-Id: I760b45b68f6012809c70c2a584e4144a99f98733

2 files changed, 14 insertions, 0 deletions

diff --git a/absl/status/internal/status_internal.h b/absl/status/internal/status_internal.h
index ac12940a..34914d2e 100644
--- a/absl/status/internal/status_internal.h
+++ b/absl/status/internal/status_internal.h
@@ -16,6 +16,7 @@
 
 #include <string>
 
+#include "absl/base/attributes.h"
 #include "absl/container/inlined_vector.h"
 #include "absl/strings/cord.h"
 
@@ -25,7 +26,14 @@ namespace absl {
 ABSL_NAMESPACE_BEGIN
 // Returned Status objects may not be ignored. Codesearch doesn't handle ifdefs
 // as part of a class definitions (b/6995610), so we use a forward declaration.
+//
+// TODO(b/176172494): ABSL_MUST_USE_RESULT should expand to the more strict
+// [[nodiscard]]. For now, just use [[nodiscard]] directly when it is available.
+#if ABSL_HAVE_CPP_ATTRIBUTE(nodiscard)
+class [[nodiscard]] Status;
+#else
 class ABSL_MUST_USE_RESULT Status;
+#endif
 ABSL_NAMESPACE_END
 }  // namespace absl
 #endif  // !SWIG
diff --git a/absl/status/statusor.h b/absl/status/statusor.h
index c051fbb3..d6ebdc2b 100644
--- a/absl/status/statusor.h
+++ b/absl/status/statusor.h
@@ -106,7 +106,13 @@ class BadStatusOrAccess : public std::exception {
 
 // Returned StatusOr objects may not be ignored.
 template <typename T>
+#if ABSL_HAVE_CPP_ATTRIBUTE(nodiscard)
+// TODO(b/176172494): ABSL_MUST_USE_RESULT should expand to the more strict
+// [[nodiscard]]. For now, just use [[nodiscard]] directly when it is available.
+class [[nodiscard]] StatusOr;
+#else
 class ABSL_MUST_USE_RESULT StatusOr;
+#endif  // ABSL_HAVE_CPP_ATTRIBUTE(nodiscard)
 
 // absl::StatusOr<T>
 //