moc: Add --debug-includes option to moc

Because moc silently ignores missing headers, or sometimes includes
the wrong header, it is useful to have a facility to print which
header paths were considered and found.

Add a new --debug-includes option that does that.

Task-number: QTBUG-101775
Change-Id: I72b294ae53d6e47252c7d8afe0f2245da78bfadb
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/tools/moc/main.cpp

@@ -306,6 +306,10 @@ int runMoc(int argc, char **argv)
     jsonOption.setDescription(QStringLiteral("In addition to generating C++ code, create a machine-readable JSON file in a file that matches the output file and an extra .json extension."));
     parser.addOption(jsonOption);
 
+    QCommandLineOption debugIncludesOption(QStringLiteral("debug-includes"));
+    debugIncludesOption.setDescription(QStringLiteral("Display debug messages of each considered include path."));
+    parser.addOption(debugIncludesOption);
+
     QCommandLineOption collectOption(QStringLiteral("collect-json"));
     collectOption.setDescription(QStringLiteral("Instead of processing C++ code, collect previously generated JSON output into a single file."));
     parser.addOption(collectOption);
@@ -358,6 +362,7 @@ int runMoc(int argc, char **argv)
 
     const bool ignoreConflictingOptions = parser.isSet(ignoreConflictsOption);
     pp.preprocessOnly = parser.isSet(preprocessOption);
+    pp.setDebugIncludes(parser.isSet(debugIncludesOption));
     if (parser.isSet(noIncludeOption)) {
         moc.noInclude = true;
         autoInclude = false;
@@ -499,6 +504,17 @@ int runMoc(int argc, char **argv)
     moc.currentFilenames.push(filename.toLocal8Bit());
     moc.includes = pp.includes;
 
+    if (Q_UNLIKELY(parser.isSet(debugIncludesOption))) {
+        fprintf(stderr, "debug-includes: include search list:\n");
+
+        for (auto &includePath : pp.includes) {
+            fprintf(stderr, "debug-includes:   '%s' framework: %d \n",
+                    includePath.path.constData(),
+                    includePath.isFrameworkPath);
+        }
+        fprintf(stderr, "debug-includes: end of search list.\n");
+    }
+
     // 1. preprocess
     const auto includeFiles = parser.values(includeOption);
     QStringList validIncludesFiles;

src/tools/moc/preprocessor.cpp

@@ -1016,9 +1016,15 @@ static void mergeStringLiterals(Symbols *_symbols)
 }
 
 static QByteArray searchIncludePaths(const QList<Parser::IncludePath> &includepaths,
-                                     const QByteArray &include)
+                                     const QByteArray &include,
+                                     const bool debugIncludes)
 {
     QFileInfo fi;
+
+    if (Q_UNLIKELY(debugIncludes)) {
+        fprintf(stderr, "debug-includes: searching for '%s'\n", include.constData());
+    }
+
     for (int j = 0; j < includepaths.size() && !fi.exists(); ++j) {
         const Parser::IncludePath &p = includepaths.at(j);
         if (p.isFrameworkPath) {
@@ -1030,6 +1036,12 @@ static QByteArray searchIncludePaths(const QList<Parser::IncludePath> &includepa
         } else {
             fi.setFile(QString::fromLocal8Bit(p.path), QString::fromLocal8Bit(include));
         }
+
+        if (Q_UNLIKELY(debugIncludes)) {
+            const auto candidate = fi.filePath().toLocal8Bit();
+            fprintf(stderr, "debug-includes: considering '%s'\n", candidate.constData());
+        }
+
         // try again, maybe there's a file later in the include paths with the same name
         // (186067)
         if (fi.isDir()) {
@@ -1038,9 +1050,20 @@ static QByteArray searchIncludePaths(const QList<Parser::IncludePath> &includepa
         }
     }
 
-    if (!fi.exists() || fi.isDir())
+    if (!fi.exists() || fi.isDir()) {
+        if (Q_UNLIKELY(debugIncludes)) {
+            fprintf(stderr, "debug-includes: can't find '%s'\n", include.constData());
+        }
         return QByteArray();
-    return fi.canonicalFilePath().toLocal8Bit();
+    }
+
+    const auto result = fi.canonicalFilePath().toLocal8Bit();
+
+    if (Q_UNLIKELY(debugIncludes)) {
+        fprintf(stderr, "debug-includes: found '%s'\n", result.constData());
+    }
+
+    return result;
 }
 
 QByteArray Preprocessor::resolveInclude(const QByteArray &include, const QByteArray &relativeTo)
@@ -1054,7 +1077,11 @@ QByteArray Preprocessor::resolveInclude(const QByteArray &include, const QByteAr
 
     auto it = nonlocalIncludePathResolutionCache.find(include);
     if (it == nonlocalIncludePathResolutionCache.end())
-       it = nonlocalIncludePathResolutionCache.insert(include, searchIncludePaths(includes, include));
+       it = nonlocalIncludePathResolutionCache.insert(include,
+                                                      searchIncludePaths(
+                                                          includes,
+                                                          include,
+                                                          debugIncludes));
     return it.value();
 }
 
@@ -1319,4 +1346,10 @@ void Preprocessor::until(Token t)
         ;
 }
 
+void Preprocessor::setDebugIncludes(bool value)
+{
+    debugIncludes = value;
+}
+
+
 QT_END_NAMESPACE

src/tools/moc/preprocessor.h

@@ -81,10 +81,13 @@ public:
     enum TokenizeMode { TokenizeCpp, TokenizePreprocessor, PreparePreprocessorStatement, TokenizePreprocessorStatement, TokenizeInclude, PrepareDefine, TokenizeDefine };
     static Symbols tokenize(const QByteArray &input, int lineNum = 1, TokenizeMode mode = TokenizeCpp);
 
+    void setDebugIncludes(bool value);
+
 private:
     void until(Token);
 
     void preprocess(const QByteArray &filename, Symbols &preprocessed);
+    bool debugIncludes = false;
 };
 
 QT_END_NAMESPACE