commit 136edb7cbf62a4878345a8f4819240a09679d5f3
from: Sven M. Hallberg <pesco@khjk.org>
date: Thu Jun 25 16:43:02 2020 UTC

improve overflow check in act_numb()

commit - 4a6cd10658be56430c4801ea6189fdbf2faf222d
commit + 136edb7cbf62a4878345a8f4819240a09679d5f3
blob - 07004141c4ea65df9faf9ac86dfc2e6223d65afd
blob + c6325722b033869d39e2520efd13b0c98ddada3e
--- pdf.c
+++ pdf.c
@@ -623,8 +623,8 @@ act_numb(const HParseResult *p, void *u)
 {
 	const HParsedToken *x = p->ast;
 	int64_t sgn = 1;
-	uint64_t toolarge = -(INT64_MIN+1); // XXX bypass not being able to negate INT64_MIN due to two's complement
-	toolarge += 1;
+	uint64_t abs_INT64_MIN = ((uint64_t) -(INT64_MIN + 1)) + 1;
+		/* equals -INT64_MIN but avoids an overflow warning */
 
 	if (x->token_type == TT_SEQUENCE) {
 		sgn = H_FIELD_SINT(0);
@@ -634,7 +634,8 @@ act_numb(const HParseResult *p, void *u)
 	assert(sgn == 1 || sgn == -1);
 	switch (x->token_type) {
 	case TT_UINT:
-		if (x->uint > toolarge)	/* would overflow */
+		if ((sgn > 0 && x->uint > INT64_MAX) ||
+		    (sgn < 0 && x->uint > abs_INT64_MIN))
 			return NULL;	// XXX structured error type
 		return H_MAKE_SINT(sgn * x->uint);
 	case TT_DOUBLE: