fix ASAN's 'applying zero offset to null pointer' v1 PROPOSED

Diogo Santos: 2
 fix ASAN's 'applying zero offset to null pointer'
 decl: fix ASAN's 'division by zero'

 3 files changed, 13 insertions(+), 8 deletions(-)

[PATCH 1/2] fix ASAN's 'applying zero offset to null pointer' Export this patch

Found with clang 18.1.6 using UndefinedBehaviorSanitizer.
---
 pp.c  |  3 ++-
 qbe.c | 16 ++++++++++------
 2 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/pp.c b/pp.c
index 99e56e8..95057b8 100644
--- a/pp.c
+++ b/pp.c
@@ -523,7 +523,8 @@ expandfunc(struct macro *m)
 		error(&t->loc, "too many arguments for macro '%s'", m->name);
 	for (i = 0, t = tok.val; i < m->nparam; ++i) {
 		arg[i].token = t;
-		t += arg[i].ntoken;
+		if (t)
+			t += arg[i].ntoken;
 	}
 	m->arg = arg;
 }
diff --git a/qbe.c b/qbe.c
index 33d6b71..383af42 100644
--- a/qbe.c
+++ b/qbe.c
@@ -550,9 +550,11 @@ delfunc(struct func *f)
 
 	while (b = f->start) {
 		f->start = b->next;
-		arrayforeach (&b->insts, inst)
-			free(*inst);
-		free(b->insts.val);
+		if (b->insts.val) {
+			arrayforeach (&b->insts, inst)
+				free(*inst);
+			free(b->insts.val);
+		}
 		free(b);
 	}
 	mapfree(&f->gotos, free);
@@ -1319,9 +1321,11 @@ emitfunc(struct func *f, bool global)
 			emitvalue(b->phi.val[1]);
 			putchar('\n');
 		}
-		instend = (struct inst **)((char *)b->insts.val + b->insts.len);
-		for (inst = b->insts.val; inst != instend;)
-			inst = emitinst(inst, instend);
+		if (b->insts.val) {
+			instend = (struct inst **)((char *)b->insts.val + b->insts.len);
+			for (inst = b->insts.val; inst != instend;)
+				inst = emitinst(inst, instend);
+		}
 		emitjump(&b->jump);
 	}
 	puts("}");
-- 
2.45.1

[PATCH 2/2] decl: fix ASAN's 'division by zero' Export this patch

Found with clang 18.1.6 using the UndefinedBehaviorSanitizer.
Test `compatible-vla-types.c`, line 15, triggers this UB.
---
 decl.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/decl.c b/decl.c
index 228c776..7bd37d8 100644
--- a/decl.c
+++ b/decl.c
@@ -698,7 +698,7 @@ declarator(struct scope *s, struct qualtype base, char **name, struct scope **fu
 				if (e->kind == EXPRCONST) {
 					if (e->type->u.basic.issigned && e->u.constant.u >> 63)
 						error(&tok.loc, "array length must be non-negative");
-					if (e->u.constant.u > ULLONG_MAX / base.type->size)
+					if (base.type->size && e->u.constant.u > ULLONG_MAX / base.type->size)
 						error(&tok.loc, "array length is too large");
 					t->size = base.type->size * e->u.constant.u;
 				} else {
-- 
2.45.1