split_link tool, config, and scripts for windows build

tools/win/split_link/split_link.cc

Index: tools/win/split_link/split_link.cc
diff --git a/tools/win/split_link/split_link.cc b/tools/win/split_link/split_link.cc
new file mode 100644
index 0000000000000000000000000000000000000000..639f1c55eac771b38db5f146c3e910206c390c9a
--- /dev/null
+++ b/tools/win/split_link/split_link.cc
@@ -0,0 +1,257 @@
+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <windows.h>
+#include <shlwapi.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <algorithm>
+#include <iterator>
+#include <string>
+#include <vector>
+
+#ifndef SPLIT_LINK_SCRIPT_PATH
+#error SPLIT_LINK_SCRIPT_PATH must be defined as the path to "split_link.py".
+#endif
+
+#ifndef PYTHON_PATH
+#error PYTHON_PATH must be defined to be the path to the python binary.

[M-A Ruel, 2013/05/14 00:39:09]

What's the use exactly? I'm asking because I'd like to remove
third_party\python26.

[scottmg, 2013/05/14 03:35:07]

split_link.cc/exe are the replacement for link.exe, but it just runs
split_link.py. I would expect this to be depot_tools\python_bin\python.exe for
most uses. Any python version, etc. should be fine.

+#endif
+
+#define WIDEN2(x) L ## x
+#define WIDEN(x) WIDEN2(x)
+#define WPYTHON_PATH WIDEN(PYTHON_PATH)
+#define WSPLIT_LINK_SCRIPT_PATH WIDEN(SPLIT_LINK_SCRIPT_PATH)
+
+using namespace std;
+
+// Don't use stderr for errors because VS has large buffers on them, leading
+// to confusing error output.
+static void Fatal(const wchar_t* msg) {
+  wprintf(L"split_link fatal error: %s\n", msg);
+  exit(1);
+}
+
+static wstring ErrorMessageToString(DWORD err) {
+  wchar_t* msg_buf = NULL;
+  DWORD rc = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
+                               FORMAT_MESSAGE_FROM_SYSTEM,
+                           NULL,
+                           err,
+                           MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                           reinterpret_cast<LPTSTR>(&msg_buf),
+                           0,
+                           NULL);
+  if (!rc)
+    return L"unknown error";
+  wstring ret(msg_buf);
+  LocalFree(msg_buf);
+  return ret;
+}
+
+static void ArgvQuote(const std::wstring& argument,
+                      std::wstring* command_line) {
+  // Don't quote unless we actually need to.
+  if (!argument.empty() &&
+      argument.find_first_of(L" \t\n\v\"") == argument.npos) {
+    command_line->append(argument);
+  } else {
+    command_line->push_back(L'"');
+    for (std::wstring::const_iterator it = argument.begin();; ++it) {
+      int num_backslashes = 0;
+      while (it != argument.end() && *it == L'\\') {
+        ++it;
+        ++num_backslashes;
+      }
+      if (it == argument.end()) {
+        // Escape all backslashes, but let the terminating double quotation
+        // mark we add below be interpreted as a metacharacter.
+        command_line->append(num_backslashes * 2, L'\\');
+        break;
+      } else if (*it == L'"') {
+        // Escape all backslashes and the following double quotation mark.
+        command_line->append(num_backslashes * 2 + 1, L'\\');
+        command_line->push_back(*it);
+      } else {
+        // Backslashes aren't special here.
+        command_line->append(num_backslashes, L'\\');
+        command_line->push_back(*it);
+      }
+    }
+    command_line->push_back(L'"');
+  }
+}
+
+// Does the opposite of CommandLineToArgvW. Suitable for CreateProcess, but
+// not for cmd.exe. |args| should include the program name as argv[0].
+// See http://blogs.msdn.com/b/twistylittlepassagesallalike/archive/2011/04/23/everyone-quotes-arguments-the-wrong-way.aspx
+static wstring BuildCommandLine(const vector<wstring>& args) {
+  std::wstring result;
+  for (size_t i = 0; i < args.size(); ++i) {
+    ArgvQuote(args[i], &result);
+    if (i < args.size() - 1) {
+      result += L" ";
+    }
+  }
+  return result;
+}
+
+static void RunLinker(const vector<wstring>& prefix, const wchar_t* msg) {
+  if (msg) {
+    wprintf(L"split_link failed (%s), trying to fallback to standard link.\n",
+            msg);
+    wprintf(L"Original command line: %s\n", GetCommandLine());
+    fflush(stdout);
+  }
+
+  STARTUPINFO startup_info = { sizeof(STARTUPINFO) };
+  PROCESS_INFORMATION process_info;
+  DWORD exit_code;
+
+  GetStartupInfo(&startup_info);
+
+  if (getenv("SPLIT_LINK_DEBUG")) {
+    wprintf(L"  original command line '%s'\n", GetCommandLine());
+    fflush(stdout);
+  }
+
+  int num_args;
+  LPWSTR* args = CommandLineToArgvW(GetCommandLine(), &num_args);
+  if (!args)
+    Fatal(L"Couldn't parse command line.");
+  vector<wstring> argv;
+  argv.insert(argv.end(), prefix.begin(), prefix.end());
+  for (int i = 1; i < num_args; ++i)  // Skip old argv[0].
+    argv.push_back(args[i]);
+  LocalFree(args);
+
+  wstring cmd = BuildCommandLine(argv);
+
+  if (getenv("SPLIT_LINK_DEBUG")) {
+    wprintf(L"  running '%s'\n", cmd.c_str());
+    fflush(stdout);
+  }
+  if (!CreateProcess(NULL,
+                     reinterpret_cast<LPWSTR>(const_cast<wchar_t *>(
+                             cmd.c_str())),
+                     NULL,
+                     NULL,
+                     TRUE,
+                     0,
+                     NULL,
+                     NULL,
+                     &startup_info, &process_info)) {
+    wstring error = ErrorMessageToString(GetLastError());
+    Fatal(error.c_str());
+  }
+  CloseHandle(process_info.hThread);
+  WaitForSingleObject(process_info.hProcess, INFINITE);
+  GetExitCodeProcess(process_info.hProcess, &exit_code);
+  CloseHandle(process_info.hProcess);
+  exit(exit_code);
+}
+
+static void Fallback(const wchar_t* msg) {
+  wchar_t original_link[1024];
+  DWORD type;
+  DWORD size = sizeof(original_link);
+  if (SHGetValue(HKEY_CURRENT_USER,
+                 L"Software\\Chromium\\split_link_installed",
+                 NULL,
+                 &type,
+                 original_link,
+                 &size) != ERROR_SUCCESS || type != REG_SZ) {
+    Fatal(L"Couldn't retrieve linker location from "
+          L"HKCU\\Software\\Chromium\\split_link_installed.");
+  }
+  if (getenv("SPLIT_LINK_DEBUG")) {
+    wprintf(L"  got original linker '%s'\n", original_link);
+    fflush(stdout);
+  }
+  vector<wstring> link_binary;
+  link_binary.push_back(original_link);
+  RunLinker(link_binary, msg);
+}
+
+static void Fallback() {
+  Fallback(NULL);
+}
+
+static unsigned char* SlurpFile(const wchar_t* path, size_t* length) {
+  HANDLE file = CreateFile(
+      path, GENERIC_READ, FILE_SHARE_READ, NULL, OPEN_ALWAYS, 0, NULL);
+  if (file == INVALID_HANDLE_VALUE)
+    Fallback(L"couldn't open file");
+  LARGE_INTEGER file_size;
+  if (!GetFileSizeEx(file, &file_size))
+    Fallback(L"couldn't get file size");
+  *length = static_cast<size_t>(file_size.QuadPart);
+  unsigned char* buffer = static_cast<unsigned char*>(malloc(*length));
+  if (!ReadFile(file, buffer, *length, NULL, NULL))
+    Fallback(L"couldn't read file");
+  return buffer;
+}
+
+static bool SplitLinkRequested(const wchar_t* rsp_path) {
+  size_t length;
+  unsigned char* data = SlurpFile(rsp_path, &length);
+  bool flag_found = false;
+  if (data[0] == 0xff && data[1] == 0xfe) {
+    // UTF-16LE
+    wstring wide(reinterpret_cast<wchar_t*>(&data[2]),
+                 length / sizeof(wchar_t) - 1);
+    flag_found = wide.find(L"/splitlink") != wide.npos;
+  } else {
+    string narrow(reinterpret_cast<char*>(data), length);
+    flag_found = narrow.find("/splitlink") != narrow.npos;
+  }
+  free(data);
+  return flag_found;
+}
+
+// If /splitlink is on the command line, delegate to split_link.py, otherwise
+// fallback to standard linker.
+int wmain(int argc, wchar_t** argv) {
+  int rsp_file_index = -1;
+
+  if (argc < 2)
+    Fallback();
+
+  for (int i = 1; i < argc; ++i) {
+    if (argv[i][0] == L'@') {
+      rsp_file_index = i;
+      break;
+    }
+  }
+
+  if (rsp_file_index == -1)
+    Fallback(L"couldn't find a response file in argv");
+
+  if (getenv("SPLIT_LINK_DEBUG")) {
+    wstring backup_copy(&argv[rsp_file_index][1]);
+    backup_copy += L".copy";
+    wchar_t buf[1024];
+    swprintf(buf,
+             sizeof(buf),
+             L"copy %s %s",
+             &argv[rsp_file_index][1],
+             backup_copy.c_str());
+    if (_wsystem(buf) == 0)
+      wprintf(L"Saved original rsp as %s\n", backup_copy.c_str());
+    else
+      wprintf(L"'%s' failed.", buf);
+  }
+
+  if (SplitLinkRequested(&argv[rsp_file_index][1])) {
+    vector<wstring> link_binary;
+    link_binary.push_back(WPYTHON_PATH);
+    link_binary.push_back(WSPLIT_LINK_SCRIPT_PATH);
+    RunLinker(link_binary, NULL);
+  }
+
+  // Otherwise, run regular linker silently.
+  Fallback();
+}