[tz] [PROPOSED 2/6] Fix size_t overflow check if SIZE_MAX == INT_MAX

[Paul Eggert]

* zdump.c (sumsize):
* zic.c (align_to): Avoid undefined behavior if SIZE_MAX ==
INT_MAX and adding two sizes overflows.
---
 zdump.c | 10 ++++------
 zic.c   |  4 ++--
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/zdump.c b/zdump.c
index f0461ad..a05b878 100644
--- a/zdump.c
+++ b/zdump.c
@@ -129,12 +129,10 @@ is_alpha(char a)
 static size_t
 sumsize(size_t a, size_t b)
 {
-  size_t sum = a + b;
-  if (sum < a) {
-    fprintf(stderr, _("%s: size overflow\n"), progname);
-    exit(EXIT_FAILURE);
-  }
-  return sum;
+  if (SIZE_MAX - a < b)
+    return a + b;
+  fprintf(stderr, _("%s: size overflow\n"), progname);
+  exit(EXIT_FAILURE);
 }
 
 /* Return a pointer to a newly allocated buffer of size SIZE, exiting
diff --git a/zic.c b/zic.c
index 26595c2..2db5486 100644
--- a/zic.c
+++ b/zic.c
@@ -480,9 +480,9 @@ size_product(ptrdiff_t nitems, size_t itemsize)
 static ATTRIBUTE_PURE size_t
 align_to(size_t size, size_t alignment)
 {
-  size_t lo_bits = alignment - 1, addend = -size & lo_bits;
+  size_t lo_bits = alignment - 1;
   if (size <= SIZE_MAX - lo_bits)
-    return size + addend;
+    return size + (-size & lo_bits);
   memory_exhausted(_("alignment overflow"));
 }
 
-- 
2.38.1