From 69a2e01edd818a76949f4f499e14feac896aad8f Mon Sep 17 00:00:00 2001
From: Avi Drissman <avi@chromium.org>
Date: Tue, 12 Dec 2023 17:44:37 +0000
Subject: Add limitations to bit_cast

Using bit_cast on pointers does not accomplish anything useful, and
obscures what might be incorrect behavior. Do not allow base::bit_cast
to be misused in that way.

Bug: 1506769
Change-Id: Ib9f3acf954c5537c7520f72827854de81afda382
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5094596
Reviewed-by: Hongchan Choi <hongchan@chromium.org>
Reviewed-by: Ilya Sherman <isherman@chromium.org>
Reviewed-by: Will Harris <wfh@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Dominic Battre <battre@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Adam Rice <ricea@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Code-Coverage: findit-for-me@appspot.gserviceaccount.com <findit-for-me@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1236404}
NOKEYCHECK=True
GitOrigin-RevId: 70cb7f749d60410db4397c0fc3b35d189ad591ab
---
 google/compression_utils.cc | 22 +++++++++++-----------
 1 file changed, 11 insertions(+), 11 deletions(-)

diff --git a/google/compression_utils.cc b/google/compression_utils.cc
index 279ea07..c2b17e4 100644
--- a/google/compression_utils.cc
+++ b/google/compression_utils.cc
@@ -4,7 +4,6 @@
 
 #include "third_party/zlib/google/compression_utils.h"
 
-#include "base/bit_cast.h"
 #include "base/check_op.h"
 #include "base/process/memory.h"
 #include "base/sys_byteorder.h"
@@ -24,8 +23,8 @@ bool GzipCompress(base::span<const char> input,
   // uLongf can be larger than size_t.
   uLongf compressed_size_long = static_cast<uLongf>(output_buffer_size);
   if (zlib_internal::GzipCompressHelper(
-          base::bit_cast<Bytef*>(output_buffer), &compressed_size_long,
-          base::bit_cast<const Bytef*>(input.data()),
+          reinterpret_cast<Bytef*>(output_buffer), &compressed_size_long,
+          reinterpret_cast<const Bytef*>(input.data()),
           static_cast<uLongf>(input.size()), malloc_fn, free_fn) != Z_OK) {
     return false;
   }
@@ -55,7 +54,7 @@ bool GzipCompress(base::span<const uint8_t> input, std::string* output) {
 
   if (zlib_internal::GzipCompressHelper(
           compressed_data, &compressed_data_size,
-          base::bit_cast<const Bytef*>(input.data()), input_size, nullptr,
+          reinterpret_cast<const Bytef*>(input.data()), input_size, nullptr,
           nullptr) != Z_OK) {
     free(compressed_data);
     return false;
@@ -82,8 +81,8 @@ bool GzipUncompress(const std::string& input, std::string* output) {
 
   uncompressed_output.resize(uncompressed_size);
   if (zlib_internal::GzipUncompressHelper(
-          base::bit_cast<Bytef*>(uncompressed_output.data()),
-          &uncompressed_size, base::bit_cast<const Bytef*>(input.data()),
+          reinterpret_cast<Bytef*>(uncompressed_output.data()),
+          &uncompressed_size, reinterpret_cast<const Bytef*>(input.data()),
           static_cast<uLongf>(input.length())) == Z_OK) {
     output->swap(uncompressed_output);
     return true;
@@ -102,8 +101,8 @@ bool GzipUncompress(base::span<const uint8_t> input,
   if (uncompressed_size > output.size())
     return false;
   return zlib_internal::GzipUncompressHelper(
-             base::bit_cast<Bytef*>(output.data()), &uncompressed_size,
-             base::bit_cast<const Bytef*>(input.data()),
+             reinterpret_cast<Bytef*>(const_cast<uint8_t*>(output.data())),
+             &uncompressed_size, reinterpret_cast<const Bytef*>(input.data()),
              static_cast<uLongf>(input.size())) == Z_OK;
 }
 
@@ -117,8 +116,8 @@ bool GzipUncompress(base::span<const uint8_t> input, std::string* output) {
   uLongf uncompressed_size = GetUncompressedSize(input);
   output->resize(uncompressed_size);
   return zlib_internal::GzipUncompressHelper(
-             base::bit_cast<Bytef*>(output->data()), &uncompressed_size,
-             base::bit_cast<const Bytef*>(input.data()),
+             reinterpret_cast<Bytef*>(output->data()), &uncompressed_size,
+             reinterpret_cast<const Bytef*>(input.data()),
              static_cast<uLongf>(input.size())) == Z_OK;
 }
 
@@ -128,7 +127,8 @@ uint32_t GetUncompressedSize(base::span<const char> compressed_data) {
 
 uint32_t GetUncompressedSize(base::span<const uint8_t> compressed_data) {
   return zlib_internal::GetGzipUncompressedSize(
-      base::bit_cast<Bytef*>(compressed_data.data()), compressed_data.size());
+      reinterpret_cast<const Bytef*>(compressed_data.data()),
+      compressed_data.size());
 }
 
 }  // namespace compression
-- 
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