[clang-tools-extra] r333993 - [clangd] Rewrite JSON dispatcher loop using C IO (FILE*) instead of std::istream.
Kostya Serebryany via cfe-commits
cfe-commits at lists.llvm.org
Fri Jun 8 12:44:47 PDT 2018
Looks like this broke the clang-fuzzer:
https://oss-fuzz-build-logs.storage.googleapis.com/index.html
Step #4: /src/llvm/tools/clang/tools/extra/clangd/fuzzer/ClangdFuzzer.cpp:31:17:
error: no viable conversion from 'std::istringstream' (aka
'basic_istringstream<char>') to 'std::FILE *' (aka '_IO_FILE *')
Step #4: LSPServer.run(In);
Step #4: ^~
Step #4: /src/llvm/tools/clang/tools/extra/clangd/fuzzer/../ClangdLSPServer.h:46:23:
note: passing argument to parameter 'In' here
Step #4: bool run(std::FILE *In,
Step #4: ^
Step #4: 1 error generated.
Step #4: ninja: build stopped: subcommand failed.
On Tue, Jun 5, 2018 at 2:38 AM Sam McCall via cfe-commits <
cfe-commits at lists.llvm.org> wrote:
> Author: sammccall
> Date: Tue Jun 5 02:34:46 2018
> New Revision: 333993
>
> URL: http://llvm.org/viewvc/llvm-project?rev=333993&view=rev
> Log:
> [clangd] Rewrite JSON dispatcher loop using C IO (FILE*) instead of
> std::istream.
>
> Summary:
> The EINTR loop around getline was added to fix an issue with mac gdb, but
> seems
> to loop infinitely in rare cases on linux where the parent editor exits
> (most
> reports with VSCode).
> I can't work out how to fix this in a portable way with std::istream, but
> the
> C APIs have clearer contracts and LLVM has a RetryAfterSignal function for
> use
> with them which seems battle-tested.
>
> While here, clean up some inconsistency around \n in log messages (now
> add it only after JSON payloads), and reduce the scope of the
> long-message handling which was only really added to fight fuzzers.
>
> Reviewers: malaperle, ilya-biryukov
>
> Subscribers: klimek, ioeric, jkorous, cfe-commits
>
> Differential Revision: https://reviews.llvm.org/D47643
>
> Modified:
> clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp
> clang-tools-extra/trunk/clangd/ClangdLSPServer.h
> clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp
> clang-tools-extra/trunk/clangd/JSONRPCDispatcher.h
> clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp
> clang-tools-extra/trunk/test/clangd/too_large.test
>
> Modified: clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp?rev=333993&r1=333992&r2=333993&view=diff
>
> ==============================================================================
> --- clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp (original)
> +++ clang-tools-extra/trunk/clangd/ClangdLSPServer.cpp Tue Jun 5 02:34:46
> 2018
> @@ -396,7 +396,7 @@ ClangdLSPServer::ClangdLSPServer(JSONOut
> SupportedSymbolKinds(defaultSymbolKinds()),
> Server(CDB, FSProvider, /*DiagConsumer=*/*this, Opts) {}
>
> -bool ClangdLSPServer::run(std::istream &In, JSONStreamStyle InputStyle) {
> +bool ClangdLSPServer::run(std::FILE *In, JSONStreamStyle InputStyle) {
> assert(!IsDone && "Run was called before");
>
> // Set up JSONRPCDispatcher.
>
> Modified: clang-tools-extra/trunk/clangd/ClangdLSPServer.h
> URL:
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clangd/ClangdLSPServer.h?rev=333993&r1=333992&r2=333993&view=diff
>
> ==============================================================================
> --- clang-tools-extra/trunk/clangd/ClangdLSPServer.h (original)
> +++ clang-tools-extra/trunk/clangd/ClangdLSPServer.h Tue Jun 5 02:34:46
> 2018
> @@ -42,8 +42,8 @@ public:
> /// class constructor. This method must not be executed more than once
> for
> /// each instance of ClangdLSPServer.
> ///
> - /// \return Wether we received a 'shutdown' request before an 'exit'
> request
> - bool run(std::istream &In,
> + /// \return Whether we received a 'shutdown' request before an 'exit'
> request.
> + bool run(std::FILE *In,
> JSONStreamStyle InputStyle = JSONStreamStyle::Standard);
>
> private:
>
> Modified: clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp?rev=333993&r1=333992&r2=333993&view=diff
>
> ==============================================================================
> --- clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp (original)
> +++ clang-tools-extra/trunk/clangd/JSONRPCDispatcher.cpp Tue Jun 5
> 02:34:46 2018
> @@ -14,6 +14,7 @@
> #include "llvm/ADT/SmallString.h"
> #include "llvm/ADT/StringExtras.h"
> #include "llvm/Support/Chrono.h"
> +#include "llvm/Support/Errno.h"
> #include "llvm/Support/SourceMgr.h"
> #include <istream>
>
> @@ -66,7 +67,7 @@ void JSONOutput::writeMessage(const json
> Outs << "Content-Length: " << S.size() << "\r\n\r\n" << S;
> Outs.flush();
> }
> - log(llvm::Twine("--> ") + S);
> + log(llvm::Twine("--> ") + S + "\n");
> }
>
> void JSONOutput::log(const Twine &Message) {
> @@ -180,27 +181,43 @@ bool JSONRPCDispatcher::call(const json:
> return true;
> }
>
> -static llvm::Optional<std::string> readStandardMessage(std::istream &In,
> +// Tries to read a line up to and including \n.
> +// If failing, feof() or ferror() will be set.
> +static bool readLine(std::FILE *In, std::string &Out) {
> + static constexpr int BufSize = 1024;
> + size_t Size = 0;
> + Out.clear();
> + for (;;) {
> + Out.resize(Size + BufSize);
> + // Handle EINTR which is sent when a debugger attaches on some
> platforms.
> + if (!llvm::sys::RetryAfterSignal(nullptr, ::fgets, &Out[Size],
> BufSize, In))
> + return false;
> + clearerr(In);
> + // If the line contained null bytes, anything after it (including \n)
> will
> + // be ignored. Fortunately this is not a legal header or JSON.
> + size_t Read = std::strlen(&Out[Size]);
> + if (Read > 0 && Out[Size + Read - 1] == '\n') {
> + Out.resize(Size + Read);
> + return true;
> + }
> + Size += Read;
> + }
> +}
> +
> +// Returns None when:
> +// - ferror() or feof() are set.
> +// - Content-Length is missing or empty (protocol error)
> +static llvm::Optional<std::string> readStandardMessage(std::FILE *In,
> JSONOutput &Out) {
> // A Language Server Protocol message starts with a set of HTTP headers,
> // delimited by \r\n, and terminated by an empty line (\r\n).
> unsigned long long ContentLength = 0;
> - while (In.good()) {
> - std::string Line;
> - std::getline(In, Line);
> - if (!In.good() && errno == EINTR) {
> - In.clear();
> - continue;
> - }
> + std::string Line;
> + while (true) {
> + if (feof(In) || ferror(In) || !readLine(In, Line))
> + return llvm::None;
>
> Out.mirrorInput(Line);
> - // Mirror '\n' that gets consumed by std::getline, but is not
> included in
> - // the resulting Line.
> - // Note that '\r' is part of Line, so we don't need to mirror it
> - // separately.
> - if (!In.eof())
> - Out.mirrorInput("\n");
> -
> llvm::StringRef LineRef(Line);
>
> // We allow comments in headers. Technically this isn't part
> @@ -208,19 +225,13 @@ static llvm::Optional<std::string> readS
> if (LineRef.startswith("#"))
> continue;
>
> - // Content-Type is a specified header, but does nothing.
> - // Content-Length is a mandatory header. It specifies the length of
> the
> - // following JSON.
> - // It is unspecified what sequence headers must be supplied in, so we
> - // allow any sequence.
> - // The end of headers is signified by an empty line.
> + // Content-Length is a mandatory header, and the only one we handle.
> if (LineRef.consume_front("Content-Length: ")) {
> if (ContentLength != 0) {
> log("Warning: Duplicate Content-Length header received. "
> "The previous value for this message (" +
> - llvm::Twine(ContentLength) + ") was ignored.\n");
> + llvm::Twine(ContentLength) + ") was ignored.");
> }
> -
> llvm::getAsUnsignedInteger(LineRef.trim(), 0, ContentLength);
> continue;
> } else if (!LineRef.trim().empty()) {
> @@ -233,46 +244,45 @@ static llvm::Optional<std::string> readS
> }
> }
>
> - // Guard against large messages. This is usually a bug in the client
> code
> - // and we don't want to crash downstream because of it.
> + // The fuzzer likes crashing us by sending "Content-Length:
> 9999999999999999"
> if (ContentLength > 1 << 30) { // 1024M
> - In.ignore(ContentLength);
> - log("Skipped overly large message of " + Twine(ContentLength) +
> - " bytes.\n");
> + log("Refusing to read message with long Content-Length: " +
> + Twine(ContentLength) + ". Expect protocol errors.");
> + return llvm::None;
> + }
> + if (ContentLength == 0) {
> + log("Warning: Missing Content-Length header, or zero-length
> message.");
> return llvm::None;
> }
>
> - if (ContentLength > 0) {
> - std::string JSON(ContentLength, '\0');
> - In.read(&JSON[0], ContentLength);
> - Out.mirrorInput(StringRef(JSON.data(), In.gcount()));
> -
> - // If the stream is aborted before we read ContentLength bytes, In
> - // will have eofbit and failbit set.
> - if (!In) {
> - log("Input was aborted. Read only " + llvm::Twine(In.gcount()) +
> - " bytes of expected " + llvm::Twine(ContentLength) + ".\n");
> + std::string JSON(ContentLength, '\0');
> + for (size_t Pos = 0, Read; Pos < ContentLength; Pos += Read) {
> + // Handle EINTR which is sent when a debugger attaches on some
> platforms.
> + Read = llvm::sys::RetryAfterSignal(0u, ::fread, &JSON[Pos], 1,
> + ContentLength - Pos, In);
> + Out.mirrorInput(StringRef(&JSON[Pos], Read));
> + if (Read == 0) {
> + log("Input was aborted. Read only " + llvm::Twine(Pos) +
> + " bytes of expected " + llvm::Twine(ContentLength) + ".");
> return llvm::None;
> }
> - return std::move(JSON);
> - } else {
> - log("Warning: Missing Content-Length header, or message has zero "
> - "length.\n");
> - return llvm::None;
> + clearerr(In); // If we're done, the error was transient. If we're not
> done,
> + // either it was transient or we'll see it again on
> retry.
> + Pos += Read;
> }
> + return std::move(JSON);
> }
>
> // For lit tests we support a simplified syntax:
> // - messages are delimited by '---' on a line by itself
> // - lines starting with # are ignored.
> // This is a testing path, so favor simplicity over performance here.
> -static llvm::Optional<std::string> readDelimitedMessage(std::istream &In,
> +// When returning None, feof() or ferror() will be set.
> +static llvm::Optional<std::string> readDelimitedMessage(std::FILE *In,
> JSONOutput &Out) {
> std::string JSON;
> std::string Line;
> - while (std::getline(In, Line)) {
> - Line.push_back('\n'); // getline() consumed the newline.
> -
> + while (readLine(In, Line)) {
> auto LineRef = llvm::StringRef(Line).trim();
> if (LineRef.startswith("#")) // comment
> continue;
> @@ -284,39 +294,47 @@ static llvm::Optional<std::string> readD
> JSON += Line;
> }
>
> - if (In.bad()) {
> + if (ferror(In)) {
> log("Input error while reading message!");
> return llvm::None;
> - } else {
> + } else { // Including EOF
> Out.mirrorInput(
> llvm::formatv("Content-Length: {0}\r\n\r\n{1}", JSON.size(),
> JSON));
> return std::move(JSON);
> }
> }
>
> -void clangd::runLanguageServerLoop(std::istream &In, JSONOutput &Out,
> +// The use of C-style std::FILE* IO deserves some explanation.
> +// Previously, std::istream was used. When a debugger attached on MacOS,
> the
> +// process received EINTR, the stream went bad, and clangd exited.
> +// A retry-on-EINTR loop around reads solved this problem, but caused
> clangd to
> +// sometimes hang rather than exit on other OSes. The interaction between
> +// istreams and signals isn't well-specified, so it's hard to get this
> right.
> +// The C APIs seem to be clearer in this respect.
> +void clangd::runLanguageServerLoop(std::FILE *In, JSONOutput &Out,
> JSONStreamStyle InputStyle,
> JSONRPCDispatcher &Dispatcher,
> bool &IsDone) {
> auto &ReadMessage =
> (InputStyle == Delimited) ? readDelimitedMessage :
> readStandardMessage;
> - while (In.good()) {
> + while (!IsDone && !feof(In)) {
> + if (ferror(In)) {
> + log("IO error: " + llvm::sys::StrError());
> + return;
> + }
> if (auto JSON = ReadMessage(In, Out)) {
> if (auto Doc = json::parse(*JSON)) {
> // Log the formatted message.
> log(llvm::formatv(Out.Pretty ? "<-- {0:2}\n" : "<-- {0}\n",
> *Doc));
> // Finally, execute the action for this JSON message.
> if (!Dispatcher.call(*Doc, Out))
> - log("JSON dispatch failed!\n");
> + log("JSON dispatch failed!");
> } else {
> // Parse error. Log the raw message.
> log(llvm::formatv("<-- {0}\n" , *JSON));
> log(llvm::Twine("JSON parse error: ") +
> - llvm::toString(Doc.takeError()) + "\n");
> + llvm::toString(Doc.takeError()));
> }
> }
> - // If we're done, exit the loop.
> - if (IsDone)
> - break;
> }
> }
>
> Modified: clang-tools-extra/trunk/clangd/JSONRPCDispatcher.h
> URL:
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clangd/JSONRPCDispatcher.h?rev=333993&r1=333992&r2=333993&view=diff
>
> ==============================================================================
> --- clang-tools-extra/trunk/clangd/JSONRPCDispatcher.h (original)
> +++ clang-tools-extra/trunk/clangd/JSONRPCDispatcher.h Tue Jun 5 02:34:46
> 2018
> @@ -102,7 +102,9 @@ enum JSONStreamStyle {
> /// if it is.
> /// Input stream(\p In) must be opened in binary mode to avoid preliminary
> /// replacements of \r\n with \n.
> -void runLanguageServerLoop(std::istream &In, JSONOutput &Out,
> +/// We use C-style FILE* for reading as std::istream has unclear
> interaction
> +/// with signals, which are sent by debuggers on some OSs.
> +void runLanguageServerLoop(std::FILE *In, JSONOutput &Out,
> JSONStreamStyle InputStyle,
> JSONRPCDispatcher &Dispatcher, bool &IsDone);
>
>
> Modified: clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp
> URL:
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp?rev=333993&r1=333992&r2=333993&view=diff
>
> ==============================================================================
> --- clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp (original)
> +++ clang-tools-extra/trunk/clangd/tool/ClangdMain.cpp Tue Jun 5 02:34:46
> 2018
> @@ -238,5 +238,5 @@ int main(int argc, char *argv[]) {
> llvm::set_thread_name("clangd.main");
> // Change stdin to binary to not lose \r\n on windows.
> llvm::sys::ChangeStdinToBinary();
> - return LSPServer.run(std::cin, InputStyle) ? 0 :
> NoShutdownRequestErrorCode;
> + return LSPServer.run(stdin, InputStyle) ? 0 :
> NoShutdownRequestErrorCode;
> }
>
> Modified: clang-tools-extra/trunk/test/clangd/too_large.test
> URL:
> http://llvm.org/viewvc/llvm-project/clang-tools-extra/trunk/test/clangd/too_large.test?rev=333993&r1=333992&r2=333993&view=diff
>
> ==============================================================================
> --- clang-tools-extra/trunk/test/clangd/too_large.test (original)
> +++ clang-tools-extra/trunk/test/clangd/too_large.test Tue Jun 5 02:34:46
> 2018
> @@ -4,4 +4,4 @@
> #
> Content-Length: 2147483648
>
> -# STDERR: Skipped overly large message
> +# STDERR: Refusing to read message
>
>
> _______________________________________________
> cfe-commits mailing list
> cfe-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
>
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