diff options
authorRich Felker <>2016-05-23 18:19:11 -0400
committerRich Felker <>2016-05-23 18:19:11 -0400
commit77baaa47e107f176fb2dc150dd6a9ad87f6cbe24 (patch)
parent81fb75a1d75c20d97292cbbe4cde6a1e65871abe (diff)
fix a64l undefined behavior on ILP32 archs, wrong results on LP64 archs
the difference of pointers is a signed type ptrdiff_t; if it is only 32-bit, left-shifting it by 30 bits produces undefined behavior. cast the difference to an appropriate unsigned type, uint32_t, before shifting to avoid this. the a64l function is specified to return a signed 32-bit result in type long. as noted in the bug report by Ed Schouten, converting implicitly from uint32_t only produces the desired result when long is a 32-bit type. since the computation has to be done in unsigned arithmetic to avoid overflow, simply cast the result to int32_t. further, POSIX leaves the behavior on invalid input unspecified but not undefined, so we should not take the difference between the potentially-null result of strchr and the base pointer without first checking the result. the simplest behavior is just returning the partial conversion already performed in this case, so do that.
1 files changed, 6 insertions, 3 deletions
diff --git a/src/misc/a64l.c b/src/misc/a64l.c
index 86aeefe0..60557710 100644
--- a/src/misc/a64l.c
+++ b/src/misc/a64l.c
@@ -9,9 +9,12 @@ long a64l(const char *s)
int e;
uint32_t x = 0;
- for (e=0; e<36 && *s; e+=6, s++)
- x |= (strchr(digits, *s)-digits)<<e;
- return x;
+ for (e=0; e<36 && *s; e+=6, s++) {
+ const char *d = strchr(digits, *s);
+ if (!d) break;
+ x |= (uint32_t)(d-digits)<<e;
+ }
+ return (int32_t)x;
char *l64a(long x0)