functions that can tail-call must be tail-called as welltail-calls

Otherwise we could "leak" stack frames, which causes crashes on platforms with small stack sizes.
This still did not result in a reproducable speedup with GCC 16.

fixup 2e097cec409182c3cb39b74489387480bf8a278f

3 files changed, 24 insertions, 20 deletions

diff --git a/src/core-commands.c b/src/core-commands.c
index d01cbb9..d850c14 100644
--- a/src/core-commands.c
+++ b/src/core-commands.c
@@ -914,10 +914,8 @@ teco_state_start_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 		/*
 		 * <CTRL/x> commands implemented in teco_state_control
 		 */
-		if (TECO_IS_CTL(chr)) {
-			teco_state_t *next = teco_state_control_input(ctx, TECO_CTL_ECHO(chr), error);
-			TECO_RETURN(ctx, next, error);
-		}
+		if (TECO_IS_CTL(chr))
+			TECO_TAIL return teco_state_control_input(ctx, TECO_CTL_ECHO(chr), error);
 	}
 
 	teco_state_t *next = teco_machine_main_transition_input(ctx, transitions, G_N_ELEMENTS(transitions),
@@ -1828,7 +1826,7 @@ TECO_DEFINE_STATE(teco_state_ascii,
  * at the expense of yet another parser state.
  */
 static teco_state_t *
-teco_return(teco_machine_main_t *ctx, GError **error)
+teco_throw_return(teco_machine_main_t *ctx, GError **error)
 {
 	g_assert(ctx->flags.mode == TECO_MODE_NORMAL);
 
@@ -1871,9 +1869,11 @@ teco_return(teco_machine_main_t *ctx, GError **error)
 static teco_state_t *
 teco_state_escape_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 {
-	if (chr == '\e' || chr == '$')
-		return ctx->flags.mode > TECO_MODE_NORMAL
-			? &teco_state_start : teco_return(ctx, error);
+	if (chr == '\e' || chr == '$') {
+		if (ctx->flags.mode > TECO_MODE_NORMAL)
+			TECO_RETURN(ctx, &teco_state_start, error);
+		return teco_throw_return(ctx, error);
+	}
 
 	/*
 	 * Alternatives: ^[, <CTRL/[>, <ESC>, $ (dollar)
@@ -1900,7 +1900,7 @@ teco_state_escape_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 	if (ctx->flags.mode == TECO_MODE_NORMAL &&
 	    !teco_expressions_discard_args(error))
 		return NULL;
-	return teco_state_start_input(ctx, chr, error);
+	TECO_TAIL return teco_state_start_input(ctx, chr, error);
 }
 
 static gboolean
@@ -1940,12 +1940,13 @@ static teco_state_t *
 teco_state_ctlc_input(teco_machine_main_t *ctx, gunichar chr, GError **error)
 {
 	switch (chr) {
-	case TECO_CTL_KEY('C'):	return teco_state_ctlc_control_input(ctx, 'C', error);
+	case TECO_CTL_KEY('C'):	TECO_TAIL return teco_state_ctlc_control_input(ctx, 'C', error);
 	case '^':		TECO_RETURN(ctx, &teco_state_ctlc_control, error);
 	}
 
-	return ctx->flags.mode > TECO_MODE_NORMAL
-		? teco_state_start_input(ctx, chr, error) : teco_return(ctx, error);
+	if (ctx->flags.mode > TECO_MODE_NORMAL)
+		TECO_TAIL return teco_state_start_input(ctx, chr, error);
+	return teco_throw_return(ctx, error);
 }
 
 static gboolean
@@ -2009,8 +2010,9 @@ teco_state_ctlc_control_input(teco_machine_main_t *ctx, gunichar chr, GError **e
 		return NULL;
 	}
 
-	return ctx->flags.mode > TECO_MODE_NORMAL
-		? teco_state_control_input(ctx, chr, error) : teco_return(ctx, error);
+	if (ctx->flags.mode > TECO_MODE_NORMAL)
+		TECO_TAIL return teco_state_control_input(ctx, chr, error);
+	return teco_throw_return(ctx, error);
 }
 
 /*
diff --git a/src/parser.h b/src/parser.h
index 75a3432..0441a9c 100644
--- a/src/parser.h
+++ b/src/parser.h
@@ -557,6 +557,8 @@ gboolean teco_machine_main_step(teco_machine_main_t *ctx,
 
 #if __has_attribute(musttail)
 
+#define TECO_TAIL __attribute__((musttail))
+
 /**
  * Transition from a teco_machine_main input_cb() to another state.
  *
@@ -608,14 +610,14 @@ gboolean teco_machine_main_step(teco_machine_main_t *ctx,
 	\
 	/* the caller's signature will not line up exactly with input_cb */ \
 	typedef teco_state_t *(*caller_t)(teco_machine_main_t *, gunichar, GError **); \
-	__attribute__((musttail)) return ((caller_t)__state->input_cb)(__ctx, chr, __error); \
+	TECO_TAIL return ((caller_t)__state->input_cb)(__ctx, chr, __error); \
 } G_STMT_END
 
 #else /* __has_attribute(musttail) */
 
-/*
- * This will effectively return into the teco_machine_main_step() loop.
- */
+/* leave it to the optimizer (may or may not tail call) */
+#define TECO_TAIL
+/* this will effectively return into the teco_machine_main_step() loop */
 #define TECO_RETURN(CTX, STATE, ERROR) return (STATE)
 
 #endif /* !__has_attribute(musttail) */
diff --git a/src/stdio-commands.c b/src/stdio-commands.c
index 94da3c7..52f1e3f 100644
--- a/src/stdio-commands.c
+++ b/src/stdio-commands.c
@@ -146,7 +146,7 @@ teco_state_print_decimal_input(teco_machine_main_t *ctx, gunichar chr, GError **
 			return NULL;
 		teco_expressions_pop_num(0);
 	}
-	return teco_state_start_input(ctx, chr, error);
+	TECO_TAIL return teco_state_start_input(ctx, chr, error);
 }
 
 /*
@@ -205,7 +205,7 @@ teco_state_print_octal_input(teco_machine_main_t *ctx, gunichar chr, GError **er
 			return NULL;
 		teco_expressions_pop_num(0);
 	}
-	return teco_state_start_input(ctx, chr, error);
+	TECO_TAIL return teco_state_start_input(ctx, chr, error);
 }
 
 /*