Fix a VLA problem

see testcase, reduced example of a situation reported by Kyryl Melekhin in https://github.com/kyx0r/neatvi/ . Problem is that setting up the VLA sp-save in a scope that isn't entered at runtime leaves traces of it in outer scopes that then try to restore the stack pointer from uninitialized slots.

Michael Matz committed 5 years ago

Commit fbef90a1 parent d6f2d584 files · +69 −12Browse files

Unified · Split

4 files

tccgen.c +18 −9
tests/tests2/123_vla_bug.c +40 −0
tests/tests2/123_vla_bug.expect +5 −0
tests/tests2/79_vla_continue.c +6 −3

tccgen.c+18−9

@@ -120,7 +120,7 @@ short nb_temp_local_vars; · 119 unmodified lines
120	120
121	121	static struct scope {
122	122	struct scope *prev;
123		− struct { int loc, num; } vla;
	123	+ struct { int loc, locorig, num; } vla;
124	124	struct { Sym *s; int n; } cl;
125	125	int bsym, csym;
126	126	Sym lstk, llstk;
@@ -7268,8 +7268,12 @@ static void vla_restore(int loc) · 7141 unmodified lines
7268	7268
7269	7269	static void vla_leave(struct scope *o)
7270	7270	{
7271		− if (o->vla.num < cur_scope->vla.num)
7272		− vla_restore(o->vla.loc);
	7271	+ struct scope c = cur_scope, v = NULL;
	7272	+ for (; c != o && c; c = c->prev)
	7273	+ if (c->vla.num)
	7274	+ v = c;
	7275	+ if (v)
	7276	+ vla_restore(v->vla.locorig);
7273	7277	}
7274	7278
7275	7279	/* ------------------------------------------------------------------------- */
@@ -7281,6 +7285,7 @@ void new_scope(struct scope *o) · 5 unmodified lines
7281	7285	o = cur_scope;
7282	7286	o->prev = cur_scope;
7283	7287	cur_scope = o;
	7288	+ cur_scope->vla.num = 0;
7284	7289
7285	7290	/* record local declaration stack position */
7286	7291	o->lstk = local_stack;
@@ -7600,7 +7605,8 @@ again: · 313 unmodified lines
7600	7605	goto block_after_label;
7601	7606
7602	7607	} else if (t == TOK_GOTO) {
7603		− vla_restore(root_scope->vla.loc);
	7608	+ if (cur_scope->vla.num)
	7609	+ vla_restore(cur_scope->vla.locorig);
7604	7610	if (tok == '*' && gnu_ext) {
7605	7611	/* computed goto */
7606	7612	next();
@@ -8566,11 +8572,14 @@ static void decl_initializer_alloc(CType type, AttributeDef ad, int r, · 959 unmodified lines
8566	8572	if (NODATA_WANTED)
8567	8573	goto no_alloc;
8568	8574
8569		− /* save current stack pointer */
8570		− if (root_scope->vla.loc == 0) {
8571		− struct scope *v = cur_scope;
8572		− gen_vla_sp_save(loc -= PTR_SIZE);
8573		− do v->vla.loc = loc; while ((v = v->prev));
	8575	+ /* save before-VLA stack pointer if needed */
	8576	+ if (cur_scope->vla.num == 0) {
	8577	+ if (cur_scope->prev && cur_scope->prev->vla.num) {
	8578	+ cur_scope->vla.locorig = cur_scope->prev->vla.loc;
	8579	+ } else {
	8580	+ gen_vla_sp_save(loc -= PTR_SIZE);
	8581	+ cur_scope->vla.locorig = loc;
	8582	+ }
8574	8583	}
8575	8584
8576	8585	vla_runtime_type_size(type, &a);

tests/tests2/123_vla_bug.c+40−0

@@ -0,0 +1,40 @@
	1	+typedef __SIZE_TYPE__ size_t;
	2	+extern int printf(const char*, ...);
	3	+extern size_t strlen(const char*);
	4	+char str[] = "blabla";
	5	+int g;
	6	+int main()
	7	+{
	8	+ //char helpme[strlen(str) + 1];
	9	+ int i = 0;
	10	+#if 0
	11	+ if (g) {
	12	+ char buf[strlen(str) + 10];
	13	+ buf[0] = 0;
	14	+ }
	15	+alabel:
	16	+ printf("default: i = %d\n", i);
	17	+#else
	18	+ for (i = 0; i < 5; i++) {
	19	+ switch (i) {
	20	+ case 10:
	21	+ if (g) {
	22	+ char buf[strlen(str) + 10];
	23	+ buf[0] = 0;
	24	+ goto do_cmd;
	25	+ }
	26	+ break;
	27	+ case 1:
	28	+ printf("reached 3\n");
	29	+ do_cmd:
	30	+ printf("after do_cmd");
	31	+ break;
	32	+ default:
	33	+ g++;
	34	+ printf("default: i = %d\n", i);
	35	+ break;
	36	+ }
	37	+ }
	38	+#endif
	39	+ return 0;
	40	+}

tests/tests2/123_vla_bug.expect+5−0

@@ -0,0 +1,5 @@
	1	+default: i = 0
	2	+reached 3
	3	+after do_cmddefault: i = 2
	4	+default: i = 3
	5	+default: i = 4

tests/tests2/79_vla_continue.c+6−3

@@ -48,11 +48,14 @@ void test3() · 47 unmodified lines
48	48	int count = 10;
49	49	void *addr[count];
50	50	while(count--) {
51		− int a[f()];
	51	+ int b[f()];
	52	+ if (count >= 0) {
	53	+ int a[f()];
52	54
53		− addr[count] = a;
	55	+ addr[count] = a;
54	56
55		− continue;
	57	+ continue;
	58	+ }
56	59	}
57	60
58	61	if(addr[9] == addr[0]) {

Fix a VLA problem

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