Fix microdump_writer and add unittest.

This adds some small fixes to the microdump writer and introduces
a unittest.

BUG=chromium:410294
R=mmandlis@chromium.org

Review URL: https://breakpad.appspot.com/2814002

git-svn-id: http://google-breakpad.googlecode.com/svn/trunk@1404 4c0a9323-5329-0410-9bdc-e9ce6186880e

Makefile.am

@@ -435,6 +435,10 @@ if ANDROID_HOST
 src_client_linux_linux_client_unittest_shlib_SOURCES += \
 	src/common/android/breakpad_getcontext.S
 endif
+if LINUX_HOST
+src_client_linux_linux_client_unittest_shlib_SOURCES += \
+	src/client/linux/microdump_writer/microdump_writer_unittest.cc
+endif
 
 src_client_linux_linux_client_unittest_shlib_CPPFLAGS = \
 	-I$(top_srcdir)/src \

Makefile.in

@@ -198,12 +198,16 @@ check_PROGRAMS = $(am__EXEEXT_4) $(am__EXEEXT_5) $(am__EXEEXT_6) \
 @DISABLE_PROCESSOR_FALSE@@SELFTEST_TRUE@am__append_17 = \
 @DISABLE_PROCESSOR_FALSE@@SELFTEST_TRUE@	src/processor/stackwalker_selftest
 
-@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__append_18 = src/common/android/breakpad_getcontext.S \
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__append_18 = \
-@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@	src/common/android/breakpad_getcontext_unittest.cc
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@	src/common/android/breakpad_getcontext.S
+
 @ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__append_19 = \
-@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@	-llog -lm
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@	src/common/android/breakpad_getcontext_unittest.cc
 
 @ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__append_20 = \
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@	-llog -lm
+
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__append_21 = \
 @ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@        -llog
 
 noinst_PROGRAMS =
@@ -582,9 +586,10 @@ am__src_client_linux_linux_client_unittest_shlib_SOURCES_DIST =  \
 	src/processor/logging.cc src/processor/minidump.cc \
 	src/processor/pathname_stripper.cc \
 	src/common/android/breakpad_getcontext.S \
+	src/client/linux/microdump_writer/microdump_writer_unittest.cc \
 	src/common/android/breakpad_getcontext_unittest.cc
-@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__objects_2 = src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext.$(OBJEXT) \
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__objects_2 = src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext.$(OBJEXT)
-@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@	src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.$(OBJEXT)
+@ANDROID_HOST_TRUE@@LINUX_HOST_TRUE@am__objects_3 = src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.$(OBJEXT)
 @LINUX_HOST_TRUE@am_src_client_linux_linux_client_unittest_shlib_OBJECTS = src/client/linux/handler/src_client_linux_linux_client_unittest_shlib-exception_handler_unittest.$(OBJEXT) \
 @LINUX_HOST_TRUE@	src/client/linux/minidump_writer/src_client_linux_linux_client_unittest_shlib-directory_reader_unittest.$(OBJEXT) \
 @LINUX_HOST_TRUE@	src/client/linux/minidump_writer/src_client_linux_linux_client_unittest_shlib-cpu_set_unittest.$(OBJEXT) \
@@ -609,7 +614,9 @@ am__src_client_linux_linux_client_unittest_shlib_SOURCES_DIST =  \
 @LINUX_HOST_TRUE@	src/processor/src_client_linux_linux_client_unittest_shlib-logging.$(OBJEXT) \
 @LINUX_HOST_TRUE@	src/processor/src_client_linux_linux_client_unittest_shlib-minidump.$(OBJEXT) \
 @LINUX_HOST_TRUE@	src/processor/src_client_linux_linux_client_unittest_shlib-pathname_stripper.$(OBJEXT) \
-@LINUX_HOST_TRUE@	$(am__objects_2)
+@LINUX_HOST_TRUE@	$(am__objects_2) \
+@LINUX_HOST_TRUE@	src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.$(OBJEXT) \
+@LINUX_HOST_TRUE@	$(am__objects_3)
 src_client_linux_linux_client_unittest_shlib_OBJECTS =  \
 	$(am_src_client_linux_linux_client_unittest_shlib_OBJECTS)
 am__DEPENDENCIES_1 =
@@ -2092,7 +2099,9 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 @LINUX_HOST_TRUE@	src/processor/logging.cc \
 @LINUX_HOST_TRUE@	src/processor/minidump.cc \
 @LINUX_HOST_TRUE@	src/processor/pathname_stripper.cc \
-@LINUX_HOST_TRUE@	$(am__append_18)
+@LINUX_HOST_TRUE@	$(am__append_18) \
+@LINUX_HOST_TRUE@	src/client/linux/microdump_writer/microdump_writer_unittest.cc \
+@LINUX_HOST_TRUE@	$(am__append_19)
 @LINUX_HOST_TRUE@src_client_linux_linux_client_unittest_shlib_CPPFLAGS = \
 @LINUX_HOST_TRUE@	-I$(top_srcdir)/src \
 @LINUX_HOST_TRUE@	-I$(top_srcdir)/src/testing/include \
@@ -2102,7 +2111,7 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 
 @LINUX_HOST_TRUE@src_client_linux_linux_client_unittest_shlib_LDFLAGS =  \
 @LINUX_HOST_TRUE@	-shared -Wl,-h,linux_client_unittest_shlib \
-@LINUX_HOST_TRUE@	$(am__append_19)
+@LINUX_HOST_TRUE@	$(am__append_20)
 @LINUX_HOST_TRUE@src_client_linux_linux_client_unittest_shlib_LDADD = \
 @LINUX_HOST_TRUE@	src/client/linux/crash_generation/crash_generation_client.o \
 @LINUX_HOST_TRUE@	src/client/linux/dump_writer_common/seccomp_unwinder.o \
@@ -2134,7 +2143,7 @@ TESTS = $(check_PROGRAMS) $(check_SCRIPTS)
 
 @LINUX_HOST_TRUE@src_client_linux_linux_client_unittest_SOURCES = 
 @LINUX_HOST_TRUE@src_client_linux_linux_client_unittest_LDFLAGS =  \
-@LINUX_HOST_TRUE@	-Wl,-rpath,'$$ORIGIN' $(am__append_20)
+@LINUX_HOST_TRUE@	-Wl,-rpath,'$$ORIGIN' $(am__append_21)
 @LINUX_HOST_TRUE@src_client_linux_linux_client_unittest_LDADD = \
 @LINUX_HOST_TRUE@	src/client/linux/linux_client_unittest_shlib
 
@@ -3529,6 +3538,9 @@ src/processor/src_client_linux_linux_client_unittest_shlib-pathname_stripper.$(O
 src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext.$(OBJEXT):  \
 	src/common/android/$(am__dirstamp) \
 	src/common/android/$(DEPDIR)/$(am__dirstamp)
+src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.$(OBJEXT):  \
+	src/client/linux/microdump_writer/$(am__dirstamp) \
+	src/client/linux/microdump_writer/$(DEPDIR)/$(am__dirstamp)
 src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.$(OBJEXT):  \
 	src/common/android/$(am__dirstamp) \
 	src/common/android/$(DEPDIR)/$(am__dirstamp)
@@ -4255,6 +4267,7 @@ distclean-compile:
 @AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/handler/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-exception_handler_unittest.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/log/$(DEPDIR)/log.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/microdump_writer/$(DEPDIR)/microdump_writer.Po@am__quote@
+@AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/minidump_writer/$(DEPDIR)/linux_core_dumper.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/minidump_writer/$(DEPDIR)/linux_dumper.Po@am__quote@
 @AMDEP_TRUE@@am__include@ @am__quote@src/client/linux/minidump_writer/$(DEPDIR)/linux_ptrace_dumper.Po@am__quote@
@@ -4911,6 +4924,20 @@ src/processor/src_client_linux_linux_client_unittest_shlib-pathname_stripper.obj
 @AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
 @am__fastdepCXX_FALSE@	$(AM_V_CXX@am__nodep@)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_client_linux_linux_client_unittest_shlib_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -c -o src/processor/src_client_linux_linux_client_unittest_shlib-pathname_stripper.obj `if test -f 'src/processor/pathname_stripper.cc'; then $(CYGPATH_W) 'src/processor/pathname_stripper.cc'; else $(CYGPATH_W) '$(srcdir)/src/processor/pathname_stripper.cc'; fi`
 
+src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.o: src/client/linux/microdump_writer/microdump_writer_unittest.cc
+@am__fastdepCXX_TRUE@	$(AM_V_CXX)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_client_linux_linux_client_unittest_shlib_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -MT src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.o -MD -MP -MF src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Tpo -c -o src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.o `test -f 'src/client/linux/microdump_writer/microdump_writer_unittest.cc' || echo '$(srcdir)/'`src/client/linux/microdump_writer/microdump_writer_unittest.cc
+@am__fastdepCXX_TRUE@	$(AM_V_at)$(am__mv) src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Tpo src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Po
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	$(AM_V_CXX)source='src/client/linux/microdump_writer/microdump_writer_unittest.cc' object='src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.o' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCXX_FALSE@	$(AM_V_CXX@am__nodep@)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_client_linux_linux_client_unittest_shlib_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -c -o src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.o `test -f 'src/client/linux/microdump_writer/microdump_writer_unittest.cc' || echo '$(srcdir)/'`src/client/linux/microdump_writer/microdump_writer_unittest.cc
+
+src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.obj: src/client/linux/microdump_writer/microdump_writer_unittest.cc
+@am__fastdepCXX_TRUE@	$(AM_V_CXX)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_client_linux_linux_client_unittest_shlib_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -MT src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.obj -MD -MP -MF src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Tpo -c -o src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.obj `if test -f 'src/client/linux/microdump_writer/microdump_writer_unittest.cc'; then $(CYGPATH_W) 'src/client/linux/microdump_writer/microdump_writer_unittest.cc'; else $(CYGPATH_W) '$(srcdir)/src/client/linux/microdump_writer/microdump_writer_unittest.cc'; fi`
+@am__fastdepCXX_TRUE@	$(AM_V_at)$(am__mv) src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Tpo src/client/linux/microdump_writer/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.Po
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	$(AM_V_CXX)source='src/client/linux/microdump_writer/microdump_writer_unittest.cc' object='src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.obj' libtool=no @AMDEPBACKSLASH@
+@AMDEP_TRUE@@am__fastdepCXX_FALSE@	DEPDIR=$(DEPDIR) $(CXXDEPMODE) $(depcomp) @AMDEPBACKSLASH@
+@am__fastdepCXX_FALSE@	$(AM_V_CXX@am__nodep@)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_client_linux_linux_client_unittest_shlib_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -c -o src/client/linux/microdump_writer/src_client_linux_linux_client_unittest_shlib-microdump_writer_unittest.obj `if test -f 'src/client/linux/microdump_writer/microdump_writer_unittest.cc'; then $(CYGPATH_W) 'src/client/linux/microdump_writer/microdump_writer_unittest.cc'; else $(CYGPATH_W) '$(srcdir)/src/client/linux/microdump_writer/microdump_writer_unittest.cc'; fi`
+
 src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.o: src/common/android/breakpad_getcontext_unittest.cc
 @am__fastdepCXX_TRUE@	$(AM_V_CXX)$(CXX) $(DEFS) $(DEFAULT_INCLUDES) $(INCLUDES) $(src_client_linux_linux_client_unittest_shlib_CPPFLAGS) $(CPPFLAGS) $(AM_CXXFLAGS) $(CXXFLAGS) -MT src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.o -MD -MP -MF src/common/android/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.Tpo -c -o src/common/android/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.o `test -f 'src/common/android/breakpad_getcontext_unittest.cc' || echo '$(srcdir)/'`src/common/android/breakpad_getcontext_unittest.cc
 @am__fastdepCXX_TRUE@	$(AM_V_at)$(am__mv) src/common/android/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.Tpo src/common/android/$(DEPDIR)/src_client_linux_linux_client_unittest_shlib-breakpad_getcontext_unittest.Po

src/client/linux/microdump_writer/microdump_writer.cc

@@ -38,9 +38,10 @@
 #include "client/linux/dump_writer_common/thread_info.h"
 #include "client/linux/dump_writer_common/ucontext_reader.h"
 #include "client/linux/handler/exception_handler.h"
+#include "client/linux/log/log.h"
 #include "client/linux/minidump_writer/linux_ptrace_dumper.h"
 #include "common/linux/linux_libc_support.h"
-#include "client/linux/log/log.h"
+#include "common/scoped_ptr.h"
 
 namespace {
 
@@ -50,10 +51,13 @@ using google_breakpad::LinuxPtraceDumper;
 using google_breakpad::MappingInfo;
 using google_breakpad::MappingList;
 using google_breakpad::RawContextCPU;
+using google_breakpad::scoped_array;
 using google_breakpad::SeccompUnwinder;
 using google_breakpad::ThreadInfo;
 using google_breakpad::UContextReader;
 
+const size_t kLineBufferSize = 2048;
+
 class MicrodumpWriter {
  public:
   MicrodumpWriter(const ExceptionHandler::CrashContext* context,
@@ -64,7 +68,10 @@ class MicrodumpWriter {
         float_state_(context ? &context->float_state : NULL),
 #endif
         dumper_(dumper),
-        mapping_list_(mappings) { }
+        mapping_list_(mappings),
+        log_line_(new char[kLineBufferSize]) {
+    log_line_.get()[0] = '\0';  // Clear out the log line buffer.
+  }
 
   ~MicrodumpWriter() { dumper_->ThreadsResume(); }
 
@@ -91,11 +98,14 @@ class MicrodumpWriter {
   // Writes one line to the system log.
   void LogLine(const char* msg) {
     logger::write(msg, my_strlen(msg));
+#if !defined(__ANDROID__)
+    logger::write("\n", 1);  // Android logger appends the \n. Linux's doesn't.
+#endif
   }
 
   // Stages the given string in the current line buffer.
   void LogAppend(const char* str) {
-    my_strlcat(log_line_, str, sizeof(log_line_));
+    my_strlcat(log_line_.get(), str, kLineBufferSize);
   }
 
   // As above (required to take precedence over template specialization below).
@@ -125,8 +135,8 @@ class MicrodumpWriter {
 
   // Writes out the current line buffer on the system log.
   void LogCommitLine() {
-    logger::write(log_line_, my_strlen(log_line_));
+    LogLine(log_line_.get());
-    my_strlcpy(log_line_, "", sizeof(log_line_));
+    my_strlcpy(log_line_.get(), "", kLineBufferSize);
   }
 
   bool DumpOSInformation() {
@@ -139,7 +149,6 @@ class MicrodumpWriter {
 #else
     const char kOSId[] = "L";
 #endif
-
     LogAppend("O ");
     LogAppend(kOSId);
     LogAppend(" \"");
@@ -162,8 +171,9 @@ class MicrodumpWriter {
     size_t stack_len;
 
     if (!dumper_->GetStackInfo(&stack, &stack_len, stack_pointer)) {
-      assert(false);
+      // The stack pointer might not be available. In this case we don't hard
-      return false;
+      // fail, just produce a (almost useless) microdump w/o a stack section.
+      return true;
     }
 
     LogAppend("S 0 ");
@@ -296,7 +306,7 @@ class MicrodumpWriter {
     LogAppend(module_identifier.data4[5]);
     LogAppend(module_identifier.data4[6]);
     LogAppend(module_identifier.data4[7]);
-    LogAppend(" ");
+    LogAppend("0 ");  // Age is always 0 on Linux.
     LogAppend(file_name);
     LogCommitLine();
   }
@@ -334,7 +344,7 @@ class MicrodumpWriter {
 #endif
   LinuxDumper* dumper_;
   const MappingList& mapping_list_;
-  char log_line_[512];
+  scoped_array<char> log_line_;
 };
 }  // namespace
 

src/client/linux/microdump_writer/microdump_writer_unittest.cc

@@ -0,0 +1,130 @@
+// Copyright (c) 2014 Google Inc.
+// All rights reserved.
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <sys/syscall.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include <string>
+
+#include "breakpad_googletest_includes.h"
+#include "client/linux/handler/exception_handler.h"
+#include "client/linux/microdump_writer/microdump_writer.h"
+#include "common/linux/eintr_wrapper.h"
+#include "common/linux/ignore_ret.h"
+#include "common/scoped_ptr.h"
+#include "common/tests/auto_tempdir.h"
+#include "common/using_std_string.h"
+
+using namespace google_breakpad;
+
+// Length of a formatted GUID string =
+// sizeof(MDGUID) * 2 + 4 (for dashes) + 1 (null terminator)
+const int kGUIDStringSize = 37;
+
+namespace {
+
+typedef testing::Test MicrodumpWriterTest;
+
+TEST(MicrodumpWriterTest, Setup) {
+  int fds[2];
+  ASSERT_NE(-1, pipe(fds));
+
+  AutoTempDir temp_dir;
+  string stderr_file = temp_dir.path() + "/stderr.log";
+  int err_fd = open(stderr_file.c_str(), O_CREAT | O_RDWR, S_IRUSR | S_IWUSR);
+  ASSERT_NE(-1, err_fd);
+
+  const pid_t child = fork();
+  if (child == 0) {
+    close(fds[1]);
+    char b;
+    IGNORE_RET(HANDLE_EINTR(read(fds[0], &b, sizeof(b))));
+    close(fds[0]);
+    syscall(__NR_exit);
+  }
+  close(fds[0]);
+
+  ExceptionHandler::CrashContext context;
+  memset(&context, 0, sizeof(context));
+
+  // Set a non-zero tid to avoid tripping asserts.
+  context.tid = child;
+
+  // Push some extra mapping to check the MappingList logic.
+  const uint32_t memory_size = sysconf(_SC_PAGESIZE);
+  const char* kMemoryName = "libfoo.so";
+  const uint8_t kModuleGUID[sizeof(MDGUID)] = {
+     0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77,
+     0x88, 0x99, 0xAA, 0xBB, 0xCC, 0xDD, 0xEE, 0xFF
+  };
+
+  MappingInfo info;
+  info.start_addr = memory_size;
+  info.size = memory_size;
+  info.offset = 42;
+  strcpy(info.name, kMemoryName);
+
+  MappingList mappings;
+  MappingEntry mapping;
+  mapping.first = info;
+  memcpy(mapping.second, kModuleGUID, sizeof(MDGUID));
+  mappings.push_back(mapping);
+
+  // Redirect temporarily stderr to the stderr.log file.
+  int save_err = dup(STDERR_FILENO);
+  ASSERT_NE(-1, save_err);
+  ASSERT_NE(-1, dup2(err_fd, STDERR_FILENO));
+
+  ASSERT_TRUE(WriteMicrodump(child, &context, sizeof(context), mappings));
+
+  // Revert stderr back to the console.
+  dup2(save_err, STDERR_FILENO);
+  close(save_err);
+
+  // Read back the stderr file and check for the microdump marker.
+  fsync(err_fd);
+  lseek(err_fd, 0, SEEK_SET);
+  const size_t kBufSize = 64 * 1024;
+  scoped_array<char> buf(new char[kBufSize]);
+  ASSERT_GT(read(err_fd, buf.get(), kBufSize), 0);
+
+  ASSERT_NE(static_cast<char*>(0), strstr(
+      buf.get(), "-----BEGIN BREAKPAD MICRODUMP-----"));
+  ASSERT_NE(static_cast<char*>(0), strstr(
+      buf.get(), "-----END BREAKPAD MICRODUMP-----"));
+  ASSERT_NE(static_cast<char*>(0), strstr(
+      buf.get(), "M 0000000000001000 000000000000002A 0000000000001000 "
+      "33221100554477668899AABBCCDDEEFF0 libfoo.so"));
+
+  close(err_fd);
+  close(fds[1]);
+}
+
+}  // namespace