Enhance C code execution by adding a wrapper to disable stdout buffering

new-backend/executor/executor.go

@@ -316,6 +316,62 @@ func (e *CodeExecutor) executeC(submission *models.CodeSubmission, tempDir strin
         return
     }
 
+    // Create a wrapper script that will include setbuf to disable buffering
+    wrapperCode := `#include <stdio.h>
+
+// Forward declaration of user's main function
+int user_main();
+
+int main() {
+    // Disable buffering completely for stdout
+    setbuf(stdout, NULL);
+    
+    // Call the user's code
+    return user_main();
+}
+
+// User's code begins here
+`
+    
+    // Modify the user's code to be a function called from our wrapper
+    modifiedCode := submission.Code
+    // Replace main function with our wrapper
+    mainRegex := regexp.MustCompile(`int\s+main\s*\([^)]*\)\s*{`)
+    if mainRegex.MatchString(modifiedCode) {
+        // Rename user's main to user_main
+        modifiedCode = mainRegex.ReplaceAllString(modifiedCode, "int user_main() {")
+        
+        // Combine wrapper with modified user code
+        finalCode := wrapperCode + modifiedCode
+        
+        // Write the final code with wrapper to file
+        if err := os.WriteFile(codeFile, []byte(finalCode), 0644); err != nil {
+            submission.Status = "failed"
+            submission.Output = "Failed to write code file: " + err.Error()
+            return
+        }
+    } else {
+        // If no main function found, create a minimal program that includes the user code
+        finalCode := `#include <stdio.h>
+
+int main() {
+    // Disable buffering completely for stdout
+    setbuf(stdout, NULL);
+    
+    // Execute the user's code
+    ` + submission.Code + `
+    
+    return 0;
+}
+`
+        // Write the final code to file
+        if err := os.WriteFile(codeFile, []byte(finalCode), 0644); err != nil {
+            submission.Status = "failed"
+            submission.Output = "Failed to write code file: " + err.Error()
+            return
+        }
+    }
+
     // Compile C code
     compileCmd := exec.Command(
         "docker", "run", "--rm",