Add argument to specify output directory

README.md

@@ -61,7 +61,12 @@ gcc <regular arguments> -fplugin=externis -fplugin-arg-externis-trace=SOME_PATH/
 # Otherwise:
 gcc <regular arguments> -fplugin=/PATH/TO/build/externis.so -fplugin-arg-externis-trace=SOME_PATH/trace.json
 ```
-If a trace output path is not given, a temporary file with the name
+Alternatively, you can specify a directory to write the files to: 
+```bash 
+gcc <regular arguments> -fplugin=/PATH/TO/build/externis.so -fplugin-arg-externis-trace-dir=SOME_PATH/
+```
+In which case the output will be written to SOME_PATH/trace_XXXXXX.json
+If a trace output path or directory is not given, a temporary file with the name
 `/tmp/trace_XXXXXX.json` will be used instead.
 
 ## License & Copyright

externis.cc

@@ -102,6 +102,7 @@ static const char *PLUGIN_NAME = "externis";
 
 bool setup_output(int argc, plugin_argument *argv) {
   const char *flag_name = "trace";
+  const char *dir_flag_name = "trace-dir";
   // TODO: Maybe make the default filename related to the source filename.
   // TODO: Validate we only compile one TU at a time.
   FILE *trace_file = nullptr;
@@ -113,22 +114,25 @@ bool setup_output(int argc, plugin_argument *argv) {
       return false;
     }
     trace_file = fdopen(fd, "w");
-  } else if (argc == 1) {
-    if (strcmp(argv[0].key, flag_name)) {
-      fprintf(stderr,
-              "Externis Error! Arguments must be -fplugin-arg-%s-%s=FILENAME",
-              PLUGIN_NAME, flag_name);
-      return false;
-    }
+  } else if (argc == 1 && !strcmp(argv[0].key, flag_name)) {
     trace_file = fopen(argv[0].value, "w");
     if (!trace_file) {
       fprintf(stderr, "Externis Error! Couldn't open %s for writing\n",
               argv[0].value);
     }
+  } else if (argc == 1 && !strcmp(argv[0].key, dir_flag_name)) {
+    std::string file_template{argv[0].value};
+    file_template += "/trace_XXXXXX.json";
+    int fd = mkstemps(file_template.data(), 5);
+    if (fd == -1) {
+      perror("Externis mkstemps error: ");
+      return false;
+    }
+    trace_file = fdopen(fd, "w");
   } else {
     fprintf(stderr,
-            "Externis Error! Arguments must be -fplugin-arg-%s-%s=FILENAME\n",
-            PLUGIN_NAME, flag_name);
+            "Externis Error! Arguments must be -fplugin-arg-%s-%s=FILENAME or -fplugin-arg-%s-%s=DIRECTORY\n",
+            PLUGIN_NAME, flag_name, PLUGIN_NAME, dir_flag_name);
     return false;
   }
   if (trace_file) {