--- a/src/Parameters.h	2026-06-11 13:48:41
+++ b/src/Parameters.h	2026-09-29 20:08:47
@@ -167,8 +167,8 @@
 class PipeCloser
 {
 public:
-    PipeCloser(const char *_runningTool, FILE *_file)
-        : runningTool(_runningTool), file(_file) {}
+    PipeCloser(const char *_runningTool, FILE *_file, bool _isPipe = true)
+        : runningTool(_runningTool), file(_file), isPipe(_isPipe) {}
     ~PipeCloser() { (void) close(); }
 
     // Issues error message to cout upon error.
@@ -182,6 +182,7 @@
 private:
     std::string runningTool;
     FILE *file;
+    bool isPipe;  // false: a plain file opened with fopen (CMOC_PREPROCESSED)
 };
 
 
--- a/src/Parameters.cpp	2026-06-12 07:09:43
+++ b/src/Parameters.cpp	2026-09-29 20:08:47
@@ -511,7 +511,12 @@
         cout << "Preprocessor command: " << cppCommand << endl;
 
     extern FILE *yyin;
-    yyin = popen(cppCommand.c_str(), "r");
+    // CMOC_PREPROCESSED=1: the input file is already the preprocessor's output, so read it directly.
+    // Used where no process can be started (WebAssembly in the browser): the preprocessor runs
+    // as its own module before this one.
+    const char *preprocessedEnv = getenv("CMOC_PREPROCESSED");
+    const bool inputIsPreprocessed = preprocessedEnv != NULL && preprocessedEnv[0] != '\0';
+    yyin = inputIsPreprocessed ? fopen(inputFilename.c_str(), "r") : popen(cppCommand.c_str(), "r");
     if (yyin == NULL)
     {
         int e = errno;
@@ -520,7 +525,7 @@
         return EXIT_FAILURE;
     }
 
-    PipeCloser preprocFileCloser("preprocessor", yyin);
+    PipeCloser preprocFileCloser("preprocessor", yyin, !inputIsPreprocessed);
 
     // If this pointer receives an instance of TranslationUnit, that instance will be
     // destroyed before leaving this function.
@@ -750,6 +755,12 @@
 {
     if (file == NULL)
         return 0;  // success: nothing to do
+    if (!isPipe)
+    {
+        fclose(file);
+        file = NULL;
+        return 0;
+    }
     int status = pclose(file);
     file = NULL;
     if (!WIFEXITED(status))