Export of internal Abseil changes

--
074a799119ac881b8b8ce59ef7a3166d1aa025ac by Tom Manshreck <shreck@google.com>:

nit: Add return info for StrCat

PiperOrigin-RevId: 278647298

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d58a2a39ab6f50266cc695506ba2e86bdb45d795 by Mark Barolak <mbar@google.com>:

Stop suppressing no-nested-anon-types warnings because there aren't actually any warnings to suppress.

PiperOrigin-RevId: 278440548

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445051bd280b9a6f608a8c80b3d7cafcc1377a03 by Abseil Team <absl-team@google.com>:

ResetThreadIdentity does not need to clear identity->waiter_state.

ResetThreadIdentity is only called by NewThreadIdentity. NewThreadIdentity is
only called by CreateThreadIdentity. CreateThreadIdentity calls
PerThreadSem::Init, which initializes identity->waiter_state, immediately after
calling NewThreadIdentity. Therefore ResetThreadIdentity does not need to clear
identity->waiter_state.
PiperOrigin-RevId: 278429844

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c2079b664d92be40d5e365abcca4e9b3505a75a6 by Abseil Team <absl-team@google.com>:

Delete the f->header.magic check in LowLevelAlloc::Free().

The f->header.magic check in LowLevelAlloc::Free() is redundant, because
AddToFreeList() will immediately perform the same check.

Also fix a typo in the comment that documents the lock requirements for
Next(). The comment should say "L >= arena->mu", which is equivalent to
EXCLUSIVE_LOCKS_REQUIRED(arena->mu).

NOTE: LowLevelAlloc::Free() performs the f->header.magic check without
holding the arena lock. This may have caused the TSAN data race warning
reported in bug 143697235.
PiperOrigin-RevId: 278414140

--
5534f35ce677165700117d868f51607ed1f0d73b by Greg Falcon <gfalcon@google.com>:

Add an internal (unsupported) PiecewiseCombiner class to allow hashing buffers piecewise.

PiperOrigin-RevId: 278388902
GitOrigin-RevId: 074a799119ac881b8b8ce59ef7a3166d1aa025ac
Change-Id: I61734850cbbb01c7585e8c736a5bb56e416512a8

1 files changed, 1 insertions, 3 deletions

diff --git a/absl/base/internal/low_level_alloc.cc b/absl/base/internal/low_level_alloc.cc
index f7314ab18998..a0638f9ea496 100644
--- a/absl/base/internal/low_level_alloc.cc
+++ b/absl/base/internal/low_level_alloc.cc
@@ -447,7 +447,7 @@ static inline uintptr_t RoundUp(uintptr_t addr, uintptr_t align) {
 // that the freelist is in the correct order, that it
 // consists of regions marked "unallocated", and that no two regions
 // are adjacent in memory (they should have been coalesced).
-// L < arena->mu
+// L >= arena->mu
 static AllocList *Next(int i, AllocList *prev, LowLevelAlloc::Arena *arena) {
   ABSL_RAW_CHECK(i < prev->levels, "too few levels in Next()");
   AllocList *next = prev->next[i];
@@ -508,8 +508,6 @@ void LowLevelAlloc::Free(void *v) {
   if (v != nullptr) {
     AllocList *f = reinterpret_cast<AllocList *>(
                         reinterpret_cast<char *>(v) - sizeof (f->header));
-    ABSL_RAW_CHECK(f->header.magic == Magic(kMagicAllocated, &f->header),
-                   "bad magic number in Free()");
     LowLevelAlloc::Arena *arena = f->header.arena;
     ArenaLock section(arena);
     AddToFreelist(v, arena);