add subprocess-spawning to msvc_helper

Rather than using subprocess.h, reimplement the subprocess code.
This allows:
1) using anonymous (instead of named) pipes
2) not using all the completion port craziness
3) printing the output as it happens
4) further variation, like adjusting the environment (in a forthcoming
   change) without affecting the main subprocess code

3 files changed, 116 insertions, 1 deletions

diff --git a/src/msvc_helper-win32.cc b/src/msvc_helper-win32.cc
index ff18e80..ac957e4 100644
--- a/src/msvc_helper-win32.cc
+++ b/src/msvc_helper-win32.cc
@@ -15,8 +15,9 @@
 #include "msvc_helper.h"
 
 #include <string.h>
+#include <windows.h>
 
-#include "string_piece.h"
+#include "util.h"
 
 // static
 string CLWrapper::FilterShowIncludes(const string& line) {
@@ -33,3 +34,98 @@ string CLWrapper::FilterShowIncludes(const string& line) {
   }
   return "";
 }
+
+int CLWrapper::Run(const string& command, string* extra_output) {
+  SECURITY_ATTRIBUTES security_attributes = {};
+  security_attributes.nLength = sizeof(SECURITY_ATTRIBUTES);
+  security_attributes.bInheritHandle = TRUE;
+
+  // Must be inheritable so subprocesses can dup to children.
+  HANDLE nul = CreateFile("NUL", GENERIC_READ,
+                          FILE_SHARE_READ | FILE_SHARE_WRITE |
+                          FILE_SHARE_DELETE,
+                          &security_attributes, OPEN_EXISTING, 0, NULL);
+  if (nul == INVALID_HANDLE_VALUE)
+    Fatal("couldn't open nul");
+
+  HANDLE stdout_read, stdout_write;
+  if (!CreatePipe(&stdout_read, &stdout_write, &security_attributes, 0))
+    Win32Fatal("CreatePipe");
+
+  if (!SetHandleInformation(stdout_read, HANDLE_FLAG_INHERIT, 0))
+    Win32Fatal("SetHandleInformation");
+
+  PROCESS_INFORMATION process_info = {};
+  STARTUPINFO startup_info = {};
+  startup_info.cb = sizeof(STARTUPINFO);
+  startup_info.hStdInput = nul;
+  startup_info.hStdError = stdout_write;
+  startup_info.hStdOutput = stdout_write;
+  startup_info.dwFlags |= STARTF_USESTDHANDLES;
+
+  if (!CreateProcessA(NULL, (char*)command.c_str(), NULL, NULL,
+                      /* inherit handles */ TRUE, 0,
+                      NULL, NULL,
+                      &startup_info, &process_info)) {
+    Win32Fatal("CreateProcess");
+  }
+
+  if (!CloseHandle(nul) ||
+      !CloseHandle(stdout_write)) {
+    Win32Fatal("CloseHandle");
+  }
+
+  // Read output of the subprocess and parse it.
+  string output;
+  DWORD read_len = 1;
+  while (read_len) {
+    char buf[64 << 10];
+    read_len = 0;
+    if (!::ReadFile(stdout_read, buf, sizeof(buf), &read_len, NULL) &&
+        GetLastError() != ERROR_BROKEN_PIPE) {
+      Win32Fatal("ReadFile");
+    }
+    output.append(buf, read_len);
+
+    // Loop over all lines in the output and process them.
+    for (;;) {
+      size_t ofs = output.find_first_of("\r\n");
+      if (ofs == string::npos)
+        break;
+      string line = output.substr(0, ofs);
+
+      string include = FilterShowIncludes(line);
+      if (!include.empty()) {
+        includes_.push_back(include);
+      } else {
+        if (extra_output) {
+          extra_output->append(line);
+          extra_output->append("\n");
+        } else {
+          printf("%s\n", line.c_str());
+        }
+      }
+
+      if (ofs < output.size() && output[ofs] == '\r')
+        ++ofs;
+      if (ofs < output.size() && output[ofs] == '\n')
+        ++ofs;
+      output = output.substr(ofs);
+    }
+  }
+
+  if (WaitForSingleObject(process_info.hProcess, INFINITE) == WAIT_FAILED)
+    Win32Fatal("WaitForSingleObject");
+
+  DWORD exit_code = 0;
+  if (!GetExitCodeProcess(process_info.hProcess, &exit_code))
+    Win32Fatal("GetExitCodeProcess");
+
+  if (!CloseHandle(stdout_read) ||
+      !CloseHandle(process_info.hProcess) ||
+      !CloseHandle(process_info.hThread)) {
+    Win32Fatal("CloseHandle");
+  }
+
+  return exit_code;
+}
diff --git a/src/msvc_helper.h b/src/msvc_helper.h
index e7c2b1a..5a657be 100644
--- a/src/msvc_helper.h
+++ b/src/msvc_helper.h
@@ -23,7 +23,16 @@ struct StringPiece;
 /// format when building with /showIncludes.  This class wraps a CL
 /// process and parses that output to extract the file list.
 struct CLWrapper {
+  /// Start a process and parse its output.  Returns its exit code.
+  /// Any non-parsed output is buffered into \a extra_output if provided,
+  /// otherwise it is printed to stdout while the process runs.
+  /// Crashes (calls Fatal()) on error.
+  int Run(const string& command, string* extra_output=NULL);
+
   /// Parse a line of cl.exe output and extract /showIncludes info.
   /// If a dependency is extracted, returns a nonempty string.
+  /// Exposed for testing.
   static string FilterShowIncludes(const string& line);
+
+  vector<string> includes_;
 };
diff --git a/src/msvc_helper_test.cc b/src/msvc_helper_test.cc
index 9eb3c89..8db4c69 100644
--- a/src/msvc_helper_test.cc
+++ b/src/msvc_helper_test.cc
@@ -30,3 +30,13 @@ TEST(MSVCHelperTest, ShowIncludes) {
             CLWrapper::FilterShowIncludes("Note: including file:    "
                                           "c:\\initspaces.h"));
 }
+
+TEST(MSVCHelperTest, Run) {
+  CLWrapper cl;
+  string output;
+  cl.Run("cmd /c \"echo foo&& echo Note: including file:  foo.h&&echo bar\"",
+         &output);
+  ASSERT_EQ("foo\nbar\n", output);
+  ASSERT_EQ(1u, cl.includes_.size());
+  ASSERT_EQ("foo.h", cl.includes_[0]);
+}