3 files changed, 83 insertions, 1 deletions

diff --git a/bfs.h b/bfs.h
index b365a53..a80ff17 100644
--- a/bfs.h
+++ b/bfs.h
@@ -49,6 +49,14 @@ struct eval_state;
 typedef bool eval_fn(const struct expr *expr, struct eval_state *state);
 
 /**
+ * Various debugging flags.
+ */
+enum debugflags {
+	/** Trace all stat() calls. */
+	DEBUG_STAT = 1 << 0,
+};
+
+/**
  * The parsed command line.
  */
 struct cmdline {
@@ -70,7 +78,10 @@ struct cmdline {
 	int maxdepth;
 
 	/** bftw() flags. */
-	int flags;
+	enum bftw_flags flags;
+
+	/** Debugging flags. */
+	enum debugflags debug;
 
 	/** The command line expression. */
 	struct expr *expr;
diff --git a/eval.c b/eval.c
index 66ba895..f69c890 100644
--- a/eval.c
+++ b/eval.c
@@ -520,6 +520,33 @@ bool eval_comma(const struct expr *expr, struct eval_state *state) {
 }
 
 /**
+ * Debug stat() calls.
+ */
+void debug_stat(const struct eval_state *state) {
+	struct BFTW *ftwbuf = state->ftwbuf;
+
+	fprintf(stderr, "fstatat(");
+	if (ftwbuf->at_fd == AT_FDCWD) {
+		fprintf(stderr, "AT_FDCWD");
+	} else {
+		size_t baselen = strlen(ftwbuf->path) - strlen(ftwbuf->at_path);
+		fprintf(stderr, "\"");
+		fwrite(ftwbuf->path, 1, baselen, stderr);
+		fprintf(stderr, "\"");
+	}
+
+	fprintf(stderr, ", \"%s\", ", ftwbuf->at_path);
+
+	if (ftwbuf->at_flags == AT_SYMLINK_NOFOLLOW) {
+		fprintf(stderr, "AT_SYMLINK_NOFOLLOW");
+	} else {
+		fprintf(stderr, "%d", ftwbuf->at_flags);
+	}
+
+	fprintf(stderr, ")\n");
+}
+
+/**
  * Type passed as the argument to the bftw() callback.
  */
 struct callback_args {
@@ -567,6 +594,10 @@ static enum bftw_action cmdline_callback(struct BFTW *ftwbuf, void *ptr) {
 		eval_expr(cmdline->expr, &state);
 	}
 
+	if ((cmdline->debug & DEBUG_STAT) && ftwbuf->statbuf) {
+		debug_stat(&state);
+	}
+
 	args->ret = state.ret;
 	return state.action;
 }
diff --git a/parse.c b/parse.c
index 8376378..fb0170b 100644
--- a/parse.c
+++ b/parse.c
@@ -336,6 +336,39 @@ static struct expr *parse_test_sdata(struct parser_state *state, const char *tes
 }
 
 /**
+ * Parse -D FLAG.
+ */
+static struct expr *parse_debug(struct parser_state *state, const char *option) {
+	struct cmdline *cmdline = state->cmdline;
+
+	const char *arg = state->argv[state->i];
+	if (!arg) {
+		pretty_error(cmdline->stderr_colors,
+		             "error: %s needs a flag.\n", option);
+		return NULL;
+	}
+
+	++state->i;
+
+	if (strcmp(arg, "help") == 0) {
+		printf("Supported debug flags:\n\n");
+
+		printf("  help:  This message.\n");
+		printf("  stat:  Trace all stat() calls.\n");
+
+		state->just_info = true;
+		return NULL;
+	} else if (strcmp(arg, "stat") == 0) {
+		cmdline->debug |= DEBUG_STAT;
+	} else {
+		pretty_warning(cmdline->stderr_colors,
+		               "warning: Unrecognized debug flag '%s'.\n\n", arg);
+	}
+
+	return new_positional_option(state);
+}
+
+/**
  * Parse -[acm]{min,time}.
  */
 static struct expr *parse_acmtime(struct parser_state *state, const char *option, enum timefield field, enum timeunit unit) {
@@ -670,6 +703,12 @@ static struct expr *parse_literal(struct parser_state *state) {
 	}
 
 	switch (arg[1]) {
+	case 'D':
+		if (strcmp(arg, "-D") == 0) {
+			return parse_debug(state, arg);
+		}
+		break;
+
 	case 'P':
 		if (strcmp(arg, "-P") == 0) {
 			cmdline->flags &= ~(BFTW_FOLLOW | BFTW_DETECT_CYCLES);
@@ -1128,6 +1167,7 @@ struct cmdline *parse_cmdline(int argc, char *argv[]) {
 	cmdline->mindepth = 0;
 	cmdline->maxdepth = INT_MAX;
 	cmdline->flags = BFTW_RECOVER;
+	cmdline->debug = 0;
 	cmdline->expr = &expr_true;
 
 	cmdline->colors = parse_colors(getenv("LS_COLORS"));