Export of internal Abseil changes

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07240ca7822d007cdcc79f2c40bd58b2c2010348 by Abseil Team <absl-team@google.com>:

Correct the comment from "AlphaNum" to "Arg".

PiperOrigin-RevId: 416139192

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adcba4a6b3763626e1db7b1e8c108b3114903557 by Martijn Vels <mvels@google.com>:

Fix NewExternalRep() to require data being non-empty, and remove nullptr return.

PiperOrigin-RevId: 416135865

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c0d14cd918fb16f15d1d84de9284b5c5ecc1f8f2 by Abseil Team <absl-team@google.com>:

Fix doc comment for absl::ascii_isprint().

The comment was incorrectly saying that it includes all whitespace.
It doesn't; the only whitespace char it includes is ' '.

PiperOrigin-RevId: 416112524

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d83327800159c07002b6865e21232a12463e02dd by Abseil Team <absl-team@google.com>:

Internal change

PiperOrigin-RevId: 416099978

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baf11e9ca42ca9140cdbf8075f971db8d65b1195 by Ilya Tokar <tokarip@google.com>:

Prevent compiler from optimizing Group_Match* benchmarks away.
Currently we benchmark single store of precomputed value.

Not all affected benchmarks show performance changes:

BM_Group_Match                                          0.53ns ± 1%  0.53ns ± 0%   -0.42%  (p=0.038 n=10+10)
BM_Group_MatchEmpty                                     0.26ns ± 1%  0.26ns ± 1%     ~     (p=1.000 n=10+10)
BM_Group_MatchEmptyOrDeleted                            0.26ns ± 1%  0.26ns ± 1%     ~     (p=0.121 n=10+10)
BM_Group_CountLeadingEmptyOrDeleted                     0.26ns ± 1%  0.45ns ± 0%  +70.05%   (p=0.000 n=10+8)
BM_Group_MatchFirstEmptyOrDeleted                       0.26ns ± 0%  0.44ns ± 1%  +65.91%    (p=0.000 n=8+9)

But inspecting the generated code shows the difference,
e. g. BM_Group_MatchFirstEmptyOrDeleted

Before:
add  $0xffffffffffffffff,%rbx
jne  30

After:
pcmpeqd  %xmm0,%xmm0
pcmpgtb  -0x30(%rbp),%xmm0
pmovmskb %xmm0,%eax
add: 0x23$0xffffffffffffffff,%rbx
jne      40
PiperOrigin-RevId: 416083515

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122fbff893dc4571b3e75e4b241eb4495b925610 by Abseil Team <absl-team@google.com>:

Put namespace guard in ABSL_DECLARE_FLAG to make declaring a flag in a namespace a compiler error instead of a linker error.

PiperOrigin-RevId: 416036072

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020fd8a20f5fa319e948846e003391fcb9e03868 by Ilya Tokar <tokarip@google.com>:

Make Cord::InlineRep::set_data unconditionally zero out memory.

Currently there is a single case where we don't zero out memory
as an optimization. Unconditional zeroing doesn't show any changes
in benchmarks, except for the unrelated improvement:

BM_CordPartialCopyToCord/1M/1              12.6ns ± 4%   12.6ns ± 4%     ~     (p=0.857 n=16+19)
BM_CordPartialCopyToCord/1M/128            44.9ns ± 7%   45.0ns ± 3%     ~     (p=0.468 n=18+17)
BM_CordPartialCopyToCord/1M/1k             64.5ns ± 4%   61.4ns ± 4%   -4.82%  (p=0.000 n=19+17)
BM_CordPartialCopyToCord/1M/8k              139ns ± 3%    128ns ±15%   -7.76%  (p=0.009 n=17+20)
BM_CordPartialCopyToCord/1M/16k             193ns ± 6%    168ns ± 6%  -13.17%  (p=0.000 n=17+17)
BM_CordPartialCopyToCord/4M/16k             199ns ± 4%    177ns ± 4%  -11.36%  (p=0.000 n=17+18)
BM_CordPartialCopyToCord/4M/32k             275ns ± 3%    250ns ± 4%   -9.00%  (p=0.000 n=18+18)
BM_CordPartialCopyToCord/4M/64k             291ns ± 4%    266ns ± 5%   -8.53%  (p=0.000 n=18+16)
BM_CordPartialCopyToCord/4M/128k            322ns ± 5%    291ns ± 4%   -9.43%  (p=0.000 n=20+18)
BM_CordPartialCopyToCord/8M/32k             281ns ± 5%    251ns ± 4%  -10.38%  (p=0.000 n=20+16)
BM_CordPartialCopyToCord/8M/64k             293ns ± 6%    267ns ± 4%   -8.87%  (p=0.000 n=16+19)
BM_CordPartialCopyToCord/8M/128k            334ns ± 3%    305ns ± 2%   -8.56%  (p=0.000 n=17+16)

This is clearly an alignmnet effect since number of the executed instructions is the same:
M_CordPartialCopyToCord/1M/1                 155 ± 0%                155 ± 0%     ~     (all samples are equal)
BM_CordPartialCopyToCord/1M/128               446 ± 0%                446 ± 0%     ~           (p=0.332 n=36+39)
BM_CordPartialCopyToCord/1M/1k                473 ± 0%                473 ± 0%     ~           (p=0.969 n=40+40)
BM_CordPartialCopyToCord/1M/8k                808 ± 0%                808 ± 0%     ~           (p=0.127 n=40+39)
BM_CordPartialCopyToCord/1M/16k               957 ± 0%                957 ± 0%     ~           (p=0.532 n=40+40)
BM_CordPartialCopyToCord/4M/16k               952 ± 0%                952 ± 0%     ~           (p=0.686 n=39+39)
BM_CordPartialCopyToCord/4M/32k             1.12k ± 0%              1.12k ± 0%     ~           (p=0.690 n=40+40)
BM_CordPartialCopyToCord/4M/64k             1.23k ± 0%              1.23k ± 0%     ~           (p=0.182 n=40+39)
BM_CordPartialCopyToCord/4M/128k            1.44k ± 0%              1.44k ± 0%     ~           (p=0.711 n=40+40)
BM_CordPartialCopyToCord/8M/32k             1.12k ± 0%              1.12k ± 0%     ~           (p=0.697 n=40+40)
BM_CordPartialCopyToCord/8M/64k             1.23k ± 0%              1.23k ± 0%   +0.00%        (p=0.049 n=40+40)
BM_CordPartialCopyToCord/8M/128k            1.44k ± 0%              1.44k ± 0%     ~           (p=0.507 n=40+40)

This makes code simpler and doesn't regress performance.

PiperOrigin-RevId: 415560574

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37305b2690b31682088749e4d62f40d7095bdc54 by Derek Mauro <dmauro@google.com>:

Internal change

PiperOrigin-RevId: 415558737

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86aaed569b9e743c1eb813a5f48def978a793db3 by Martijn Vels <mvels@google.com>:

Internal change

PiperOrigin-RevId: 415515201

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6cdb8786cdcb4fa0b8a4b72fc98940877d1fdeff by Abseil Team <absl-team@google.com>:

Update SubmitMutexProfileData to accept wait_cycles instead of wait_timestamp

PiperOrigin-RevId: 415360871

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9f979d307aa16ad09f214e04876cbe84395c0901 by Abseil Team <absl-team@google.com>:

absl::flat_hash_set compiles with -Wconversion -Wsign-compare

PiperOrigin-RevId: 415357498

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9eceb14174708f15e61259d449b214a8a4c7f9e7 by Abseil Team <absl-team@google.com>:

Fix AddressIsReadable for the corner case of (aligned) addr == NULL.

PiperOrigin-RevId: 415307792

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1a39ffe55898375e2d7f88c17c99db5a1b95b313 by Martijn Vels <mvels@google.com>:

Internal change

PiperOrigin-RevId: 415162872

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64378549b110d5f5762185a5906c520fba70f0e7 by Abseil Team <absl-team@google.com>:

Fix a typo in the comments

PiperOrigin-RevId: 415088461

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41aae8322e913b82710153c22b97c611fdb6e1fb by Abseil Team <absl-team@google.com>:

Switch from `connect` to `rt_sigreturn` -- the latter is much less problematic
for system call sandboxes.

PiperOrigin-RevId: 415073965

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870c5e3388b6a35611bff538626fe7a1c8c87171 by Abseil Team <absl-team@google.com>:

Add ABSL_HAVE_HWADDRESS_SANITIZER and ABSL_HAVE_LEAK_SANITIZER

PiperOrigin-RevId: 414871189

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f213ed60a66b58da7ac40555adfb1d529ff0a4db by Derek Mauro <dmauro@google.com>:

Remove reference to __SANITIZE_MEMORY__, which does not exist

It appears to have been copied by pattern matching from the ASAN/TSAN
code blocks.

https://github.com/gcc-mirror/gcc/blob/f47662204de27f7685699eeef89aa173ccf32d85/gcc/cppbuiltin.c#L79-L126

PiperOrigin-RevId: 414806587

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b152891e73ab515f397ceb53f66c8ee2f33863ea by Abseil Team <absl-team@google.com>:

Rollback previous commit: SYS_open is not defined in certain environments.

PiperOrigin-RevId: 414521820

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5a1cbb282331023902e1374dd0d920c4effbe47f by Abseil Team <absl-team@google.com>:

Use syscall(SYS_open, ...) instead of open() to avoid possible symbol
interposition.

Also add some warning notes.

PiperOrigin-RevId: 414508186

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1824d6593612710aafdc599a89b0adced7d787f6 by Abseil Team <absl-team@google.com>:

Correct aarch64 macro check

The macro is __aarch64__, not __arch64__.

PiperOrigin-RevId: 414446225

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a1536a57b64dfd53945d33a01cfc08b18c99c97b by Abseil Team <absl-team@google.com>:

Fix backwards comment in the last commit.

PiperOrigin-RevId: 414281214

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11ac021ba779513667a31cf2563ddafc57d6d913 by Abseil Team <absl-team@google.com>:

AddressIsReadable() didn't work correctly on ARM when the given pointer was
misaligned at the end of the page.

Fix that by aligning the pointer on an 8-byte boundary before checking it.

PiperOrigin-RevId: 414203863
GitOrigin-RevId: 07240ca7822d007cdcc79f2c40bd58b2c2010348
Change-Id: If5f129194d59f5c9e5d84efd8cd9e17a70e072ab

1 files changed, 5 insertions, 1 deletions

diff --git a/absl/flags/declare.h b/absl/flags/declare.h
index b9794d8b..a791b667 100644
--- a/absl/flags/declare.h
+++ b/absl/flags/declare.h
@@ -60,6 +60,10 @@ ABSL_NAMESPACE_END
 // The ABSL_DECLARE_FLAG(type, name) macro expands to:
 //
 //   extern absl::Flag<type> FLAGS_name;
-#define ABSL_DECLARE_FLAG(type, name) extern ::absl::Flag<type> FLAGS_##name
+#define ABSL_DECLARE_FLAG(type, name)                        \
+  extern absl::Flag<type> FLAGS_##name;                      \
+  namespace absl /* block flags in namespaces */ {}          \
+  /* second redeclaration is to allow applying attributes */ \
+  extern absl::Flag<type> FLAGS_##name
 
 #endif  // ABSL_FLAGS_DECLARE_H_