Export of internal Abseil changes

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167cd2647144583746311129b0cc98a89a9897e1 by Andy Soffer <asoffer@google.com>:

Internal Changes

PiperOrigin-RevId: 268000987

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ab44fea7dfdaf763c69609a08ddfac22480ce520 by Derek Mauro <dmauro@google.com>:

Fix flags Cmake tests on Windows

PiperOrigin-RevId: 267859442

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d7ec9f7611370b01bc9a5aed7e18460df2a15429 by Abseil Team <absl-team@google.com>:

Fix undefined behavior in symbolize_elf.inc

PiperOrigin-RevId: 267684904

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e7c5f8e472a91ed99bdf4876942f2bda5751aa6c by Abseil Team <absl-team@google.com>:

Turn off ABSL_HAS_ALARM on Fuchsia.

PiperOrigin-RevId: 267666090

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b7d25d5c71a49e697a8bf6440ed30f2e3f036420 by Chris Kennelly <ckennelly@google.com>:

Mark once initialization function as no inline.

We expect this code to run infrequently.

PiperOrigin-RevId: 267649713

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dc2a5e5f1e39a03fff837d34a319033fde55d9ba by Derek Mauro <dmauro@google.com>:

Fix the MSVC CMake random build

PiperOrigin-RevId: 267624074

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ba2751b67fa17d1b6c53e5ba79f81a5371e4a03a by Abseil Team <absl-team@google.com>:

Move "internal/flag.*" files to the "internal" build target.

PiperOrigin-RevId: 267588996

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05b985a33eec4f8acff1809ad9218a1e22220f34 by Abseil Team <absl-team@google.com>:

Move "internal/flag.*" files to the "internal" build target.

PiperOrigin-RevId: 267580412
GitOrigin-RevId: 167cd2647144583746311129b0cc98a89a9897e1
Change-Id: Ibd334f46a5671c7c1d3fcf5354029e2fbb7ba91f

1 files changed, 10 insertions, 3 deletions

diff --git a/absl/debugging/symbolize_elf.inc b/absl/debugging/symbolize_elf.inc
index e73052135c98..14f0c9723a33 100644
--- a/absl/debugging/symbolize_elf.inc
+++ b/absl/debugging/symbolize_elf.inc
@@ -624,6 +624,13 @@ static bool InSection(const void *address, const ElfW(Shdr) * section) {
   return start <= address && address < (start + size);
 }
 
+static const char *ComputeOffset(const char *base, ptrdiff_t offset) {
+  // Note: cast to uintptr_t to avoid undefined behavior when base evaluates to
+  // zero and offset is non-zero.
+  return reinterpret_cast<const char *>(
+      reinterpret_cast<uintptr_t>(base) + offset);
+}
+
 // Read a symbol table and look for the symbol containing the
 // pc. Iterate over symbols in a symbol table and look for the symbol
 // containing "pc".  If the symbol is found, and its name fits in
@@ -676,7 +683,8 @@ static ABSL_ATTRIBUTE_NOINLINE FindSymbolResult FindSymbol(
       // We keep the original address for opd redirection below.
       const char *const original_start_address =
           reinterpret_cast<const char *>(symbol.st_value);
-      const char *start_address = original_start_address + relocation;
+      const char *start_address =
+          ComputeOffset(original_start_address, relocation);
 
       if (deref_function_descriptor_pointer &&
           InSection(original_start_address, opd)) {
@@ -688,8 +696,7 @@ static ABSL_ATTRIBUTE_NOINLINE FindSymbolResult FindSymbol(
 
       // If pc is inside the .opd section, it points to a function descriptor.
       const size_t size = pc_in_opd ? kFunctionDescriptorSize : symbol.st_size;
-      const void *const end_address =
-          reinterpret_cast<const char *>(start_address) + size;
+      const void *const end_address = ComputeOffset(start_address, size);
       if (symbol.st_value != 0 &&  // Skip null value symbols.
           symbol.st_shndx != 0 &&  // Skip undefined symbols.
 #ifdef STT_TLS