gh-48: Add -private mode.

Author: python-processing-unit

docs/SPECIFICATION.html

@@ -467,6 +467,8 @@
 
 - Verbose tracebacks: if the `-verbose` flag is supplied on the command line, tracebacks include the environment snapshots described in Section 10.8. In concise traceback mode the `-verbose` flag causes the interpreter to attach an `env_snapshot` entry to each frame shown; in verbose traceback mode the same flag expands the printed `State snapshot: blocks to include the selected local environment and any small set of globals included by policy. The snapshot contents follow the requirements in Section 10.2 and are suitable for deterministic replay.
 
+- Private mode: if the `-private` flag is supplied on the command line, the interpreter MUST disable the state logger and suppress environment snapshots in tracebacks. Tracebacks MUST still be emitted (concise or verbose as requested) but MUST omit any `env_snapshot` content and must not emit state-log entries; the traceback should clearly indicate when snapshot information has been suppressed.
+
 Notes:
 
 - The interpreter MAY support additional flags and a different ordering of arguments; the rules above define the semantics for `argv[1]`, `-source`, and `-verbose` specifically and are intended to be stable for tooling and replay purposes.

src/interpreter.c

@@ -89,6 +89,7 @@ static void trace_pop_frame(Interpreter* interp) {
 
 static void trace_log_step(Interpreter* interp, Stmt* stmt, Env* env) {
     if (!interp || !stmt) return;
+    if (interp->private_mode) return;
     if (interp->trace_stack_count == 0) {
         if (trace_push_frame(interp, "<top-level>", env ? env : interp->global_env, 0, 0, 0) != 0) return;
     }
@@ -176,7 +177,7 @@ char* interpreter_format_traceback(Interpreter* interp, const char* error_msg, i
             trace_append(&out, &len, &cap, row);
             snprintf(row, sizeof(row), "    State log index: %d  State id: %s\n", frame->last_step_index, frame->state_id);
             trace_append(&out, &len, &cap, row);
-            if (interp->verbose) {
+            if (interp->verbose && !interp->private_mode) {
                 char* snap = trace_env_snapshot(frame->env);
                 if (snap && snap[0] != '\0') {
                     trace_append(&out, &len, &cap, "    Env snapshot: ");
@@ -204,7 +205,7 @@ void interpreter_reset_traceback(Interpreter* interp, Env* top_env) {
     interp->trace_next_step_index = 0;
     snprintf(interp->trace_last_state_id, sizeof(interp->trace_last_state_id), "seed");
     interp->trace_last_rule[0] = '\0';
-    if (top_env) {
+    if (top_env && !interp->private_mode) {
         (void)trace_push_frame(interp, "<top-level>", top_env, 0, 0, 0);
     }
 }
@@ -2736,7 +2737,7 @@ static ExecResult exec_stmt_list(Interpreter* interp, StmtList* list, Env* env,
 
 // ============ Main entry point ============
 
-void interpreter_init(Interpreter* interp, const char* source_path, bool verbose) {
+void interpreter_init(Interpreter* interp, const char* source_path, bool verbose, bool private_mode) {
     if (!interp) return;
     memset(interp, 0, sizeof(*interp));
     interp->global_env = env_create(NULL);
@@ -2746,6 +2747,7 @@ void interpreter_init(Interpreter* interp, const char* source_path, bool verbose
     interp->modules = NULL;
     interp->current_thr = NULL;
     interp->verbose = verbose ? 1 : 0;
+    interp->private_mode = private_mode ? 1 : 0;
     interp->source_path = source_path ? strdup(source_path) : NULL;
     interp->trace_stack = NULL;
     interp->trace_stack_count = 0;
@@ -2754,9 +2756,11 @@ void interpreter_init(Interpreter* interp, const char* source_path, bool verbose
     snprintf(interp->trace_last_state_id, sizeof(interp->trace_last_state_id), "seed");
     interp->trace_last_rule[0] = '\0';
 
-    if (trace_push_frame(interp, "<top-level>", interp->global_env, 0, 0, 0) != 0) {
-        fprintf(stderr, "Out of memory\n");
-        exit(1);
+    if (!interp->private_mode) {
+        if (trace_push_frame(interp, "<top-level>", interp->global_env, 0, 0, 0) != 0) {
+            fprintf(stderr, "Out of memory\n");
+            exit(1);
+        }
     }
 
     builtins_init();
@@ -2820,7 +2824,7 @@ void interpreter_destroy(Interpreter* interp) {
 
 ExecResult exec_program(Stmt* program, const char* source_path) {
     Interpreter interp;
-    interpreter_init(&interp, source_path, false);
+    interpreter_init(&interp, source_path, false, false);
 
     LabelMap labels = {0};
     ExecResult res = exec_stmt_list(&interp, &program->as.block, interp.global_env, &labels);

src/interpreter.h

@@ -94,6 +94,7 @@ typedef struct Interpreter {
     bool isolate_env_writes;
     // Traceback/logging state
     int verbose;
+    int private_mode;
     char* source_path;
     TraceFrame* trace_stack;
     size_t trace_stack_count;
@@ -105,7 +106,7 @@ typedef struct Interpreter {
 
 // Initialize/destroy a reusable interpreter session.
 // `source_path` sets the primary module source label (e.g. script path or "<repl>").
-void interpreter_init(Interpreter* interp, const char* source_path, bool verbose);
+void interpreter_init(Interpreter* interp, const char* source_path, bool verbose, bool private_mode);
 void interpreter_destroy(Interpreter* interp);
 
 // Main entry point

src/main.c

@@ -204,9 +204,9 @@ static void repl_update_line_state(const char* line, int* brace_depth, int* line
     *line_continuation = (end > 0 && line[end - 1] == '^') ? 1 : 0;
 }
 
-static int run_repl(int verbose) {
+static int run_repl(int verbose, int private_flag) {
     Interpreter interp;
-    interpreter_init(&interp, "<repl>", verbose != 0);
+    interpreter_init(&interp, "<repl>", verbose != 0, private_flag != 0);
 
     char* entry = NULL;
     size_t entry_len = 0;
@@ -282,6 +282,7 @@ int main(int argc, char** argv) {
     int source_mode = 0;
     char* source_text = NULL;
     int verbose_flag = 0;
+    int private_flag = 0;
     int explicit_ext_count = 0;
 
     builtins_reset_dynamic();
@@ -306,6 +307,11 @@ int main(int argc, char** argv) {
             continue;
         }
 
+        if (strcmp(arg, "-private") == 0) {
+            private_flag = 1;
+            continue;
+        }
+
         if (strcmp(arg, "-source") == 0) {
             if (i + 1 >= argc) {
                 fprintf(stderr, "Missing argument for -source\n");
@@ -435,7 +441,7 @@ int main(int argc, char** argv) {
     }
 
     if (!path && !source_mode) {
-        int repl_rc = run_repl(verbose_flag);
+        int repl_rc = run_repl(verbose_flag, private_flag);
         extensions_shutdown();
         builtins_reset_dynamic();
         return repl_rc;
@@ -530,7 +536,7 @@ int main(int argc, char** argv) {
     }
 
     Interpreter interp;
-    interpreter_init(&interp, source_label, verbose_flag != 0);
+    interpreter_init(&interp, source_label, verbose_flag != 0, private_flag != 0);
     ExecResult res = exec_program_in_env(&interp, program, interp.global_env);
     interpreter_destroy(&interp);
     if (res.status == EXEC_ERROR) {