win: Add and use a custom CaptureContext() implementation

client/capture_context_mac_test.cc

Index: client/capture_context_mac_test.cc
diff --git a/client/capture_context_mac_test.cc b/client/capture_context_mac_test.cc
index 5b0b643e3ef69b0a80b53d1a9832f091bd95dd0f..436ac5ada9103df948b60acd231ab9d27ebb6d9e 100644
--- a/client/capture_context_mac_test.cc
+++ b/client/capture_context_mac_test.cc
@@ -32,13 +32,13 @@ namespace {
 // fatal gtest assertions. For other fields, where it’s possible to reason about
 // their validity based solely on their contents, sanity-checks via nonfatal
 // gtest assertions.
-void SanityCheckContext(NativeCPUContext* context) {
+void SanityCheckContext(const NativeCPUContext& context) {
 #if defined(ARCH_CPU_X86)
-  ASSERT_EQ(x86_THREAD_STATE32, context->tsh.flavor);
-  ASSERT_EQ(implicit_cast<int>(x86_THREAD_STATE32_COUNT), context->tsh.count);
+  ASSERT_EQ(x86_THREAD_STATE32, context.tsh.flavor);
+  ASSERT_EQ(implicit_cast<int>(x86_THREAD_STATE32_COUNT), context.tsh.count);
 #elif defined(ARCH_CPU_X86_64)
-  ASSERT_EQ(x86_THREAD_STATE64, context->tsh.flavor);
-  ASSERT_EQ(implicit_cast<int>(x86_THREAD_STATE64_COUNT), context->tsh.count);
+  ASSERT_EQ(x86_THREAD_STATE64, context.tsh.flavor);
+  ASSERT_EQ(implicit_cast<int>(x86_THREAD_STATE64_COUNT), context.tsh.count);
 #endif
 
 #if defined(ARCH_CPU_X86_FAMILY)
@@ -47,46 +47,46 @@ void SanityCheckContext(NativeCPUContext* context) {
   // that the high bits are all clear.
   //
   // Many bit positions in the flags register are reserved and will always read
-  // a known value. Most reservd bits are always 0, but bit 1 is always 1. Check
-  // that the reserved bits are all set to their expected values. Note that the
-  // set of reserved bits may be relaxed over time with newer CPUs, and that
-  // this test may need to be changed to reflect these developments. The current
-  // set of reserved bits are 1, 3, 5, 15, and 22 and higher. See Intel Software
-  // Developer’s Manual, Volume 1: Basic Architecture (253665-051), 3.4.3
-  // “EFLAGS Register”, and AMD Architecture Programmer’s Manual, Volume 2:
-  // System Programming (24593-3.24), 3.1.6 “RFLAGS Register”.
+  // a known value. Most reserved bits are always 0, but bit 1 is always 1.
+  // Check that the reserved bits are all set to their expected values. Note
+  // that the set of reserved bits may be relaxed over time with newer CPUs, and
+  // that this test may need to be changed to reflect these developments. The
+  // current set of reserved bits are 1, 3, 5, 15, and 22 and higher. See Intel
+  // Software Developer’s Manual, Volume 1: Basic Architecture (253665-051),
+  // 3.4.3 “EFLAGS Register”, and AMD Architecture Programmer’s Manual, Volume
+  // 2: System Programming (24593-3.24), 3.1.6 “RFLAGS Register”.
 #if defined(ARCH_CPU_X86)
-  EXPECT_EQ(0u, context->uts.ts32.__cs & ~0xffff);
-  EXPECT_EQ(0u, context->uts.ts32.__ds & ~0xffff);
-  EXPECT_EQ(0u, context->uts.ts32.__es & ~0xffff);
-  EXPECT_EQ(0u, context->uts.ts32.__fs & ~0xffff);
-  EXPECT_EQ(0u, context->uts.ts32.__gs & ~0xffff);
-  EXPECT_EQ(0u, context->uts.ts32.__ss & ~0xffff);
-  EXPECT_EQ(2u, context->uts.ts32.__eflags & 0xffc0802a);
+  EXPECT_EQ(0u, context.uts.ts32.__cs & ~0xffff);
+  EXPECT_EQ(0u, context.uts.ts32.__ds & ~0xffff);
+  EXPECT_EQ(0u, context.uts.ts32.__es & ~0xffff);
+  EXPECT_EQ(0u, context.uts.ts32.__fs & ~0xffff);
+  EXPECT_EQ(0u, context.uts.ts32.__gs & ~0xffff);
+  EXPECT_EQ(0u, context.uts.ts32.__ss & ~0xffff);
+  EXPECT_EQ(2u, context.uts.ts32.__eflags & 0xffc0802a);
 #elif defined(ARCH_CPU_X86_64)
-  EXPECT_EQ(0u, context->uts.ts64.__cs & ~UINT64_C(0xffff));
-  EXPECT_EQ(0u, context->uts.ts64.__fs & ~UINT64_C(0xffff));
-  EXPECT_EQ(0u, context->uts.ts64.__gs & ~UINT64_C(0xffff));
-  EXPECT_EQ(2u, context->uts.ts64.__rflags & UINT64_C(0xffffffffffc0802a));
+  EXPECT_EQ(0u, context.uts.ts64.__cs & ~UINT64_C(0xffff));
+  EXPECT_EQ(0u, context.uts.ts64.__fs & ~UINT64_C(0xffff));
+  EXPECT_EQ(0u, context.uts.ts64.__gs & ~UINT64_C(0xffff));
+  EXPECT_EQ(2u, context.uts.ts64.__rflags & UINT64_C(0xffffffffffc0802a));
 #endif
 #endif
 }
 
 // A CPU-independent function to return the program counter.
-uintptr_t ProgramCounterFromContext(NativeCPUContext* context) {
+uintptr_t ProgramCounterFromContext(const NativeCPUContext& context) {
 #if defined(ARCH_CPU_X86)
-  return context->uts.ts32.__eip;
+  return context.uts.ts32.__eip;
 #elif defined(ARCH_CPU_X86_64)
-  return context->uts.ts64.__rip;
+  return context.uts.ts64.__rip;
 #endif
 }
 
 // A CPU-independent function to return the stack pointer.
-uintptr_t StackPointerFromContext(NativeCPUContext* context) {
+uintptr_t StackPointerFromContext(const NativeCPUContext& context) {
 #if defined(ARCH_CPU_X86)
-  return context->uts.ts32.__esp;
+  return context.uts.ts32.__esp;
 #elif defined(ARCH_CPU_X86_64)
-  return context->uts.ts64.__rsp;
+  return context.uts.ts64.__rsp;
 #endif
 }
 
@@ -96,13 +96,13 @@ void TestCaptureContext() {
 
   {
     SCOPED_TRACE("context_1");
-    ASSERT_NO_FATAL_FAILURE(SanityCheckContext(&context_1));
+    ASSERT_NO_FATAL_FAILURE(SanityCheckContext(context_1));
   }
 
   // The program counter reference value is this function’s address. The
   // captured program counter should be slightly greater than or equal to the
   // reference program counter.
-  uintptr_t pc = ProgramCounterFromContext(&context_1);
+  uintptr_t pc = ProgramCounterFromContext(context_1);
 #if !__has_feature(address_sanitizer)
   // AddressSanitizer can cause enough code bloat that the “nearby” check would
   // likely fail.
@@ -125,7 +125,7 @@ void TestCaptureContext() {
                         reinterpret_cast<uintptr_t>(&context_2)),
                std::min(reinterpret_cast<uintptr_t>(&pc),
                         reinterpret_cast<uintptr_t>(&sp)));
-  sp = StackPointerFromContext(&context_1);
+  sp = StackPointerFromContext(context_1);
   EXPECT_LT(kReferenceSP - sp, 512u);
 
   // Capture the context again, expecting that the stack pointer stays the same
@@ -136,11 +136,11 @@ void TestCaptureContext() {
 
   {
     SCOPED_TRACE("context_2");
-    ASSERT_NO_FATAL_FAILURE(SanityCheckContext(&context_2));
+    ASSERT_NO_FATAL_FAILURE(SanityCheckContext(context_2));
   }
 
-  EXPECT_EQ(sp, StackPointerFromContext(&context_2));
-  EXPECT_GT(ProgramCounterFromContext(&context_2), pc);
+  EXPECT_EQ(sp, StackPointerFromContext(context_2));
+  EXPECT_GT(ProgramCounterFromContext(context_2), pc);
 }
 
 TEST(CaptureContextMac, CaptureContext) {