added command-line option --cpp-probe to probe headers and extension-less files for Emacs marker [skip ci]

Author: firewave

cli/cmdlineparser.cpp

@@ -544,6 +544,10 @@ CmdLineParser::Result CmdLineParser::parseFromArgs(int argc, const char* const a
                 }
             }
 
+            else if (std::strcmp(argv[i], "--cpp-probe") == 0) {
+                mSettings.cppProbe = true;
+            }
+
             // Show --debug output after the first simplifications
             else if (std::strcmp(argv[i], "--debug") == 0 ||
                      std::strcmp(argv[i], "--debug-normal") == 0)
@@ -887,6 +891,10 @@ CmdLineParser::Result CmdLineParser::parseFromArgs(int argc, const char* const a
                     return Result::Fail;
             }
 
+            else if (std::strcmp(argv[i], "--no-cpp-probe") == 0) {
+                mSettings.cppProbe = false;
+            }
+
             // Write results in file
             else if (std::strncmp(argv[i], "--output-file=", 14) == 0)
                 mSettings.outputFile = Path::simplifyPath(Path::fromNativeSeparators(argv[i] + 14));

lib/cppcheck.cpp

@@ -182,7 +182,7 @@ static void createDumpFile(const Settings& settings,
     case Standards::Language::None:
     {
         // TODO: error out on unknown language?
-        const Standards::Language lang = Path::identify(filename);
+        const Standards::Language lang = Path::identify(filename, settings.cppProbe);
         if (lang == Standards::Language::CPP)
             language = " language=\"cpp\"";
         else if (lang == Standards::Language::C)
@@ -420,7 +420,7 @@ unsigned int CppCheck::checkClang(const std::string &path)
         mErrorLogger.reportOut(std::string("Checking ") + path + " ...", Color::FgGreen);
 
     // TODO: this ignores the configured language
-    const bool isCpp = Path::identify(path) == Standards::Language::CPP;
+    const bool isCpp = Path::identify(path, mSettings.cppProbe) == Standards::Language::CPP;
     const std::string langOpt = isCpp ? "-x c++" : "-x c";
     const std::string analyzerInfo = mSettings.buildDir.empty() ? std::string() : AnalyzerInformation::getAnalyzerInfoFile(mSettings.buildDir, path, emptyString);
     const std::string clangcmd = analyzerInfo + ".clang-cmd";

lib/path.cpp

@@ -24,7 +24,9 @@
 #include "utils.h"
 
 #include <algorithm>
+#include <cstdio>
 #include <cstdlib>
+#include <memory>
 #include <sys/stat.h>
 #include <unordered_set>
 #include <utility>
@@ -235,7 +237,7 @@ bool Path::isCPP(const std::string &path)
 bool Path::acceptFile(const std::string &path, const std::set<std::string> &extra)
 {
     bool header = false;
-    return (identify(path, &header) != Standards::Language::None && !header) || extra.find(getFilenameExtension(path)) != extra.end();
+    return (identify(path, false, &header) != Standards::Language::None && !header) || extra.find(getFilenameExtension(path)) != extra.end();
 }
 
 // cppcheck-suppress unusedFunction
@@ -245,13 +247,59 @@ bool Path::isHeader(const std::string &path)
     return startsWith(extension, ".h");
 }
 
-Standards::Language Path::identify(const std::string &path, bool *header)
+#include <iostream>
+
+static bool hasEmacsCppMarker(const char* path)
+{
+    FILE *fp = fopen(path, "rt");
+    if (!fp)
+        return false;
+    std::unique_ptr<FILE, decltype(&fclose)> fp_deleter(fp, fclose);
+    std::string buf(1024, '\0');
+    if (fgets(const_cast<char*>(buf.data()), buf.size(), fp) == nullptr)
+        return false;
+    // TODO: check if line is a comment
+    const auto pos1 = buf.find("-*-");
+    if (pos1 == std::string::npos)
+        return false;
+    const auto pos2 = buf.find("-*-", pos1 + 3);
+    // TODO: make sure we read the whole line before bailing out
+    if (pos2 == std::string::npos)
+        return false;
+
+    std::cout /*<< path << " -*/ << "Emacs marker: '"  << buf.substr(pos1, (pos2 + 3) - pos1) << "'" << std::endl;
+
+    // there are more variations with lowercase and no whitespaces
+    // -*- C++ -*-
+    // -*- Mode: C++; -*-
+    // -*- Mode: C++; c-basic-offset: 8 -*-
+    const auto marker = trim(buf.substr(pos1 + 3, pos2 - pos1 - 3), " ");
+    // TODO: support extended format with "mode: C++;" and "Mode: C++;"
+    if (marker == "C++" || marker == "c++")
+        return true;
+
+    //if (marker == "C" || marker == "c")
+    //    return false;
+    std::cout << path << " - unmatched Emacs marker: '"  << marker << "'" << std::endl;
+
+    return false;
+}
+
+Standards::Language Path::identify(const std::string &path, bool cppProbe, bool *header)
 {
     // cppcheck-suppress uninitvar - TODO: FP
     if (header)
         *header = false;
 
     std::string ext = getFilenameExtension(path);
+    // standard library headers have no extension
+    if (cppProbe && ext.empty()) {
+        if (hasEmacsCppMarker(path.c_str())) {
+            if (header)
+                *header = true;
+            return Standards::Language::CPP;
+        }
+    }
     if (ext == ".C")
         return Standards::Language::CPP;
     if (c_src_exts.find(ext) != c_src_exts.end())
@@ -262,7 +310,9 @@ Standards::Language Path::identify(const std::string &path, bool *header)
     if (ext == ".h") {
         if (header)
             *header = true;
-        return Standards::Language::C; // treat as C for now
+        if (cppProbe && hasEmacsCppMarker(path.c_str()))
+            return Standards::Language::CPP;
+        return Standards::Language::C;
     }
     if (cpp_src_exts.find(ext) != cpp_src_exts.end())
         return Standards::Language::CPP;
@@ -277,7 +327,7 @@ Standards::Language Path::identify(const std::string &path, bool *header)
 bool Path::isHeader2(const std::string &path)
 {
     bool header;
-    (void)Path::identify(path, &header);
+    (void)identify(path, false, &header);
     return header;
 }
 

lib/path.h

@@ -187,10 +187,11 @@ class CPPCHECKLIB Path {
     /**
      * @brief Identify the language based on the file extension
      * @param path filename to check. path info is optional
+     * @param cppProbe check optional Emacs marker to idengtify headers as C++
      * @param header if provided indicates if the file is a header
      * @return the language type
      */
-    static Standards::Language identify(const std::string &path, bool *header = nullptr);
+    static Standards::Language identify(const std::string &path, bool cppProbe, bool *header = nullptr);
 
     /**
      * @brief Get filename without a directory path part.

lib/preprocessor.cpp

@@ -684,7 +684,7 @@ static simplecpp::DUI createDUI(const Settings &mSettings, const std::string &cf
     dui.includes = mSettings.userIncludes;  // --include
     // TODO: use mSettings.standards.stdValue instead
     // TODO: error out on unknown language?
-    const Standards::Language lang = Path::identify(filename);
+    const Standards::Language lang = Path::identify(filename, mSettings.cppProbe);
     if (lang == Standards::Language::CPP) {
         dui.std = mSettings.standards.getCPP();
         splitcfg(mSettings.platform.getLimitsDefines(Standards::getCPP(dui.std)), dui.defines, "");

lib/settings.h

@@ -167,6 +167,9 @@ class CPPCHECKLIB WARN_UNUSED Settings {
     /** cppcheck.cfg: About text */
     std::string cppcheckCfgAbout;
 
+    /** @brief check Emacs marker to detect header files as C++ */
+    bool cppProbe{};
+
     /** @brief Are we running from DACA script? */
     bool daca{};
 

lib/tokenlist.cpp

@@ -95,7 +95,7 @@ void TokenList::determineCppC()
 {
     // only try to determine if it wasn't enforced
     if (mLang == Standards::Language::None) {
-        mLang = Path::identify(getSourceFilePath());
+        mLang = Path::identify(getSourceFilePath(), mSettings ? mSettings->cppProbe : false);
         // TODO: cannot enable assert as this might occur for unknown extensions
         //ASSERT_LANG(mLang != Standards::Language::None);
         if (mLang == Standards::Language::None) {

test/cli/other_test.py

@@ -1357,4 +1357,33 @@ def test_rule(tmpdir):
     lines = stderr.splitlines()
     assert lines == [
         "{}:4:0: style: found 'f' [rule]".format(test_file)
-    ]
+    ]
+
+
+def test_cpp_probe(tmpdir):
+    test_file = os.path.join(tmpdir, 'test.h')
+    with open(test_file, 'wt') as f:
+        f.writelines([
+            'class A {};'
+        ])
+
+    args = ['-q', '--template=simple', '--cpp-probe', test_file]
+    err_lines = [
+        "{}:1:1: error: Code 'classA{{' is invalid C code. Use --std or --language to configure the language. [syntaxError]".format(test_file)
+    ]
+
+    assert_cppcheck(args, ec_exp=0, err_exp=err_lines, out_exp=[])
+
+
+def test_cpp_probe_2(tmpdir):
+    test_file = os.path.join(tmpdir, 'test.h')
+    with open(test_file, 'wt') as f:
+        f.writelines([
+            '// -*- C++ -*-',
+            'class A {};'
+        ])
+
+    # TODO: the probing is performed twice
+    args = ['-q', '--template=simple', '--cpp-probe', test_file]
+
+    assert_cppcheck(args, ec_exp=0, err_exp=[], out_exp=[])

test/cli/testutils.py

@@ -163,7 +163,7 @@ def assert_cppcheck(args, ec_exp=None, out_exp=None, err_exp=None, env=None):
         assert exitcode == ec_exp, stdout
     if out_exp is not None:
         out_lines = stdout.splitlines()
-        assert out_lines == out_exp, stdout
+        assert out_lines == out_exp, out_lines
     if err_exp is not None:
         err_lines = stderr.splitlines()
-        assert err_lines == err_exp, stderr
+        assert err_lines == err_exp, err_lines

test/testcmdlineparser.cpp

@@ -387,6 +387,10 @@ class TestCmdlineParser : public TestFixture {
         TEST_CASE(checkLevelNormal);
         TEST_CASE(checkLevelExhaustive);
         TEST_CASE(checkLevelUnknown);
+        TEST_CASE(cppProbe);
+        TEST_CASE(cppProbe2);
+        TEST_CASE(noCppProbe);
+        TEST_CASE(noCppProbe2);
 
         TEST_CASE(ignorepaths1);
         TEST_CASE(ignorepaths2);
@@ -2603,6 +2607,34 @@ class TestCmdlineParser : public TestFixture {
         ASSERT_EQUALS("cppcheck: error: unknown '--check-level' value 'default'.\n", logger->str());
     }
 
+    void cppProbe() {
+        REDIRECT;
+        const char * const argv[] = {"cppcheck", "--cpp-probe", "file.cpp"};
+        ASSERT_EQUALS(CmdLineParser::Result::Success, parser->parseFromArgs(3, argv));
+        ASSERT_EQUALS(true, settings->cppProbe);
+    }
+
+    void cppProbe2() {
+        REDIRECT;
+        const char * const argv[] = {"cppcheck", "--no-cpp-probe", "--cpp-probe", "file.cpp"};
+        ASSERT_EQUALS(CmdLineParser::Result::Success, parser->parseFromArgs(4, argv));
+        ASSERT_EQUALS(true, settings->cppProbe);
+    }
+
+    void noCppProbe() {
+        REDIRECT;
+        const char * const argv[] = {"cppcheck", "--no-cpp-probe", "file.cpp"};
+        ASSERT_EQUALS(CmdLineParser::Result::Success, parser->parseFromArgs(3, argv));
+        ASSERT_EQUALS(false, settings->cppProbe);
+    }
+
+    void noCppProbe2() {
+        REDIRECT;
+        const char * const argv[] = {"cppcheck", "--cpp-probe", "--no-cpp-probe", "file.cpp"};
+        ASSERT_EQUALS(CmdLineParser::Result::Success, parser->parseFromArgs(4, argv));
+        ASSERT_EQUALS(false, settings->cppProbe);
+    }
+
     void ignorepaths1() {
         REDIRECT;
         const char * const argv[] = {"cppcheck", "-isrc", "file.cpp"};