UnrealEngineUWP/Engine/Source/Developer/Windows/LiveCodingServer/Private/External/LC_Compiler.cpp

// Copyright 2011-2019 Molecular Matters GmbH, all rights reserved.

#include "LC_Compiler.h"
#include "LC_StringUtil.h"
#include "LC_FileUtil.h"
#include "LC_Process.h"
#include "LC_Environment.h"
#include "LC_CriticalSection.h"
#include "LC_Logging.h"
#include "LC_TimeStamp.h"


namespace
{
	// simple key-value cache for storing environment blocks for certain compilers
	class CompilerEnvironmentCache
	{
	public:
		CompilerEnvironmentCache(void)
			: m_cache(16u)
		{
		}

		~CompilerEnvironmentCache(void)
		{
			for (auto it = m_cache.begin(); it != m_cache.end(); ++it)
			{
				process::Environment* env = it->second;
				process::DestroyEnvironment(env);
			}
		}

		void Insert(const wchar_t* key, process::Environment* value)
		{
	        // BEGIN EPIC MOD - Allow passing environment block for linker
			auto it = m_cache.find(key);
			if (it != m_cache.end())
			{
				process::DestroyEnvironment(it->second);
				it->second = value;
				return;
			}
			// END EPIC MOD

			m_cache[key] = value;
		}

		const process::Environment* Fetch(const wchar_t* key)
		{
			const auto it = m_cache.find(key);
			if (it != m_cache.end())
			{
				return it->second;
			}

			return nullptr;
		}

	private:
		types::unordered_map<std::wstring, process::Environment*> m_cache;
	};

	static CompilerEnvironmentCache g_compilerEnvironmentCache;

	static CriticalSection g_compilerCacheCS;


	static std::vector<const wchar_t*> DetermineRelativePathToVcvarsFile(const wchar_t* absolutePathToCompilerExe)
	{
		// COMPILER SPECIFIC: Visual Studio. other compilers and linkers don't need vcvars*.bat to be invoked.
		std::vector<const wchar_t*> paths;
		paths.reserve(5u);

		// find out which vcvars*.bat file we have to call, based on the path to the compiler used.
		// make sure to carry out the comparison with lowercase strings only.
		wchar_t lowercaseAbsolutePathToCompilerExe[MAX_PATH] = {};
		wcscpy_s(lowercaseAbsolutePathToCompilerExe, absolutePathToCompilerExe);
		_wcslwr_s(lowercaseAbsolutePathToCompilerExe);

		// Visual Studio 2017 and above
		if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"bin\\hostx86\\x86"))
		{
			paths.push_back(L"\\..\\..\\..\\..\\..\\..\\Auxiliary\\Build\\vcvars32.bat");
		}
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"bin\\hostx86\\x64"))
		{
			paths.push_back(L"\\..\\..\\..\\..\\..\\..\\Auxiliary\\Build\\vcvarsx86_amd64.bat");
		}
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"bin\\hostx64\\x64"))
		{
			paths.push_back(L"\\..\\..\\..\\..\\..\\..\\Auxiliary\\Build\\vcvars64.bat");
		}
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"bin\\hostx64\\x86"))
		{
			paths.push_back(L"\\..\\..\\..\\..\\..\\..\\Auxiliary\\Build\\vcvarsamd64_x86.bat");
		}

		// Visual Studio 2015 and below
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"vc\\bin\\amd64_x86"))
		{
			paths.push_back(L"\\vcvarsamd64_x86.bat");
		}
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"vc\\bin\\x86_amd64"))
		{
			paths.push_back(L"\\vcvarsx86_amd64.bat");
		}
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"vc\\bin\\amd64"))
		{
			paths.push_back(L"\\vcvars64.bat");
		}
		else if (string::Contains(lowercaseAbsolutePathToCompilerExe, L"vc\\bin"))
		{
			paths.push_back(L"\\vcvars32.bat");
		}

		// fallback for toolchains which are not installed at the default location.
		// in this case, we assume the vcvars*.bat file is in the same directory and try all different flavours later.
		else
		{
			paths.push_back(L"\\vcvars64.bat");
			paths.push_back(L"\\vcvarsamd64_x86.bat");
			paths.push_back(L"\\vcvarsx86_amd64.bat");
			paths.push_back(L"\\vcvars32.bat");
		}

		return paths;
	}
}


const process::Environment* compiler::CreateEnvironmentCacheEntry(const wchar_t* absolutePathToCompilerExe)
{
	LC_LOG_DEV("Creating environment cache entry for %S", absolutePathToCompilerExe);

	// COMPILER SPECIFIC: Visual Studio. other compilers and linkers don't need vcvars*.bat to be invoked.
	{
		// bail out early in case this is the LLVM/clang/lld toolchain
		const std::wstring& toolFilename = file::GetFilename(absolutePathToCompilerExe);
		if (string::Matches(toolFilename.c_str(), L"lld.exe"))
		{
			return nullptr;
		}
		else if (string::Matches(toolFilename.c_str(), L"lld-link.exe"))
		{
			return nullptr;
		}
		else if (string::Matches(toolFilename.c_str(), L"ld.lld.exe"))
		{
			return nullptr;
		}
		else if (string::Matches(toolFilename.c_str(), L"ld64.lld.exe"))
		{
			return nullptr;
		}
	}

	const std::wstring& path = file::GetDirectory(absolutePathToCompilerExe);

	// get all possible paths to vcvars*.bat files and check which one is available
	const std::vector<const wchar_t*>& relativePathsToVcvarsFile = DetermineRelativePathToVcvarsFile(absolutePathToCompilerExe);
	for (size_t i = 0u; i < relativePathsToVcvarsFile.size(); ++i)
	{
		std::wstring pathToVcvars(path);
		pathToVcvars += relativePathsToVcvarsFile[i];

		LC_LOG_DEV("Trying vcvars*.bat at %S", pathToVcvars.c_str());

		const file::Attributes& attributes = file::GetAttributes(pathToVcvars.c_str());
		if (file::DoesExist(attributes))
		{
			// this is the correct vcvars*.bat.
			// we need to invoke the command shell, run the .bat file, and extract the process' environment to cache it for later use.
			// this is slightly more complicated than it needs to be, because we cannot simply run a command in the shell and grab
			// the environment without knowing if the .bat has finished running. similarly, we cannot grab the environment once
			// the shell process has terminated already.
			// here's what we do:
			// - create a unique, temporary file. this is used for letting the shell signal that it has finished executing
			// - run the .bat file in the shell
			// - tell the shell to delete the temporary file and pause
			// - wait until the temporary file is deleted. it is now save to grab the environment
			// - grab the environment and store it in our cache
			// - terminate the shell process

			// create an empty temporary file
			const std::wstring& tempFileDeletedByCmd = file::GenerateTempFilename();
			char emptyData = 0u;
			file::CreateFileWithData(tempFileDeletedByCmd.c_str(), &emptyData, 0u);

			// tell cmd.exe to execute commands, and quote all filenames involved.
			// the whole command needs to be quoted as well.
			const std::wstring& cmdPath = environment::GetVariable(L"COMSPEC", L"cmd");
			std::wstring commandLine(L"/c \"\"");
			commandLine += pathToVcvars;
			commandLine += L"\" && del /q \"";
			commandLine += tempFileDeletedByCmd;
			commandLine += L"\" && pause \"";

			process::Context* vcvarsProcess = process::Spawn(cmdPath.c_str(), nullptr, commandLine.c_str(), nullptr, process::SpawnFlags::NO_WINDOW);

			// wait until the temporary file is deleted.
			// busy waiting like this is not very nice, but happens only once or twice during startup, and is called from a separate thread anyway.
			const uint64_t startTimestamp = timeStamp::Get();
			bool shownWarning = false;
			for (;;)
			{
				const file::Attributes& tempAttributes = file::GetAttributes(tempFileDeletedByCmd.c_str());
				if (file::DoesExist(tempAttributes))
				{
					thread::Sleep(10u);
				}
				else
				{
					break;
				}

				// show a warning in case this takes longer than 5 seconds.
				// this can happen for some users:
				// https://developercommunity.visualstudio.com/content/problem/51179/vsdevcmdbat-or-vcvarsallbat-excecution-takes-a-ver.html
				const uint64_t delta = timeStamp::Get() - startTimestamp;
				if ((timeStamp::ToSeconds(delta) >= 5.0) && (!shownWarning))
				{
					LC_WARNING_USER("Prewarming compiler/linker environment for %S is taking suspiciously long.", pathToVcvars.c_str());
					shownWarning = true;
				}
			}

			// grab the environment from the process and insert it into the cache
			process::Environment* environment = process::CreateEnvironment(vcvarsProcess->pi.hProcess);
			{
				CriticalSection::ScopedLock lock(&g_compilerCacheCS);
				g_compilerEnvironmentCache.Insert(absolutePathToCompilerExe, environment);
			}

			process::Terminate(vcvarsProcess->pi.hProcess);
			process::Destroy(vcvarsProcess);

			return environment;
		}
		else
		{
			LC_LOG_DEV("%S does not exist", pathToVcvars.c_str());
		}
	}

	LC_WARNING_USER("Cannot determine vcvars*.bat environment for compiler/linker %S", absolutePathToCompilerExe);
	return nullptr;
}


const process::Environment* compiler::GetEnvironmentFromCache(const wchar_t* absolutePathToCompilerExe)
{
	CriticalSection::ScopedLock lock(&g_compilerCacheCS);
	return g_compilerEnvironmentCache.Fetch(absolutePathToCompilerExe);
}


const process::Environment* compiler::UpdateEnvironmentCache(const wchar_t* absolutePathToCompilerExe)
{
	const process::Environment* environment = GetEnvironmentFromCache(absolutePathToCompilerExe);
	if (environment)
	{
		return environment;
	}

	return CreateEnvironmentCacheEntry(absolutePathToCompilerExe);
}

// BEGIN EPIC MOD - Allow passing environment block for linker
void compiler::AddEnvironmentToCache(const wchar_t* absolutePathToCompilerExe, process::Environment* environment)
{
	CriticalSection::ScopedLock lock(&g_compilerCacheCS);
	g_compilerEnvironmentCache.Insert(absolutePathToCompilerExe, environment);
}
// END EPIC MOD