commit 29dc778e03ddb43081f5ec4f6245497e9a490835
author Mark Mentovai <mark@chromium.org> Tue Sep 01 20:21:15 2020 -0400
committer Copybara-Service <copybara-worker@google.com> Tue Jan 19 07:14:58 2021 -0800
tree 0194baf52c3c8bc4d10f7a030d2ac6a7da46c950
parent d3cd4c9b882be565c7a583c36d6a35ba5e556176

mac: Don’t build 32-bit ProcessReaderMac support where it’s unusable

There is no possibility to run 32-bit processes on macOS 10.15 or later.
There is never any possibility to run 32-bit processes on macOS on
arm64.

This transforms ProcessReaderMac::Is64Bit into a compile-time constant
“yes” when building for a system that will never see a 32-bit process.
This is a lightweight way to get much 32-bit support code removed from
optimized compiled output, including all of process_types. In an
optimized build of crashpad_handler for arm64, this is a 3% reduction
from 569kB to 552kB (-17kB).

Change-Id: Ib93eaa6d1bc7f19067889dd8ef261d1ef1966573
Reviewed-on: https://chromium-review.googlesource.com/c/crashpad/crashpad/+/2389010
Commit-Queue: Mark Mentovai <mark@chromium.org>
Reviewed-by: Robert Sesek <rsesek@chromium.org>
GitOrigin-RevId: df12d57e97b42e25f7ebde2e4ff3429e9c34a3d8

snapshot/mac/process_reader_mac.cc

diff --git a/snapshot/mac/process_reader_mac.cc b/snapshot/mac/process_reader_mac.cc
index fafa615..821fe3c 100644
--- a/snapshot/mac/process_reader_mac.cc
+++ b/snapshot/mac/process_reader_mac.cc
@@ -95,9 +95,12 @@
       process_memory_(),
       task_(TASK_NULL),
       initialized_(),
+#if defined(CRASHPAD_MAC_32_BIT_SUPPORT)
       is_64_bit_(false),
+#endif  // CRASHPAD_MAC_32_BIT_SUPPORT
       initialized_threads_(false),
-      initialized_modules_(false) {}
+      initialized_modules_(false) {
+}
 
 ProcessReaderMac::~ProcessReaderMac() {
   for (const Thread& thread : threads_) {
@@ -117,7 +120,12 @@
     return false;
   }
 
+#if defined(CRASHPAD_MAC_32_BIT_SUPPORT)
   is_64_bit_ = process_info_.Is64Bit();
+#else  // CRASHPAD_MAC_32_BIT_SUPPORT
+  DCHECK(process_info_.Is64Bit());
+#endif  // CRASHPAD_MAC_32_BIT_SUPPORT
+
   task_ = task;
 
   INITIALIZATION_STATE_SET_VALID(initialized_);

snapshot/mac/process_reader_mac.h

diff --git a/snapshot/mac/process_reader_mac.h b/snapshot/mac/process_reader_mac.h
index ac57a06..2f8ea9d 100644
--- a/snapshot/mac/process_reader_mac.h
+++ b/snapshot/mac/process_reader_mac.h
@@ -15,6 +15,7 @@
 #ifndef CRASHPAD_SNAPSHOT_MAC_PROCESS_READER_MAC_H_
 #define CRASHPAD_SNAPSHOT_MAC_PROCESS_READER_MAC_H_
 
+#include <Availability.h>
 #include <mach/mach.h>
 #include <stdint.h>
 #include <sys/time.h>
@@ -31,6 +32,14 @@
 #include "util/posix/process_info.h"
 #include "util/process/process_memory_mac.h"
 
+#if defined(ARCH_CPU_32_BIT) ||  \
+    (!defined(ARCH_CPU_ARM64) && \
+     __MAC_OS_X_VERSION_MIN_REQUIRED < __MAC_10_15)
+// There’s no 32-bit x86 environment on macOS 10.15 or later, and there’s no
+// 32-bit ARM environment for macOS at all.
+#define CRASHPAD_MAC_32_BIT_SUPPORT 1
+#endif  // ARCH_CPU_32_BIT || (!ARCH_CPU_ARM64 && DT < 10.15)
+
 namespace crashpad {
 
 class MachOImageReader;
@@ -116,7 +125,11 @@
   bool Initialize(task_t task);
 
   //! \return `true` if the target task is a 64-bit process.
+#if defined(CRASHPAD_MAC_32_BIT_SUPPORT) || DOXYGEN
   bool Is64Bit() const { return is_64_bit_; }
+#else  // CRASHPAD_MAC_32_BIT_SUPPORT
+  bool Is64Bit() const { return true; }
+#endif  // CRASHPAD_MAC_32_BIT_SUPPORT
 
   //! \return The target task’s process ID.
   pid_t ProcessID() const { return process_info_.ProcessID(); }
@@ -240,10 +253,12 @@
   task_t task_;  // weak
   InitializationStateDcheck initialized_;
 
+#if defined(CRASHPAD_MAC_32_BIT_SUPPORT)
   // This shadows a method of process_info_, but it’s accessed so frequently
   // that it’s given a first-class field to save a call and a few bit operations
   // on each access.
   bool is_64_bit_;
+#endif  // CRASHPAD_MAC_32_BIT_SUPPORT
 
   bool initialized_threads_;
   bool initialized_modules_;