Sema: Warn on sizeof on binary ops on decayed arrays.
The array will decay into a pointer, creating an unexpected result.
sizeof(array + int) is an easy to make typo for sizeof(array) + int.
This was motivated by a NetBSD security bug, used sizeof(key - r) instead of
sizeof(key) - r, reducing entropy in a random number generator.
http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/kern/subr_cprng.c.diff?r1=1.14&r2=1.15&only_with_tag=MAIN&f=h
Differential Revision: http://llvm-reviews.chandlerc.com/D571
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178371 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/warn-sizeof-array-decay.c b/test/Sema/warn-sizeof-array-decay.c
new file mode 100644
index 0000000..cc3ee1d
--- /dev/null
+++ b/test/Sema/warn-sizeof-array-decay.c
@@ -0,0 +1,18 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void f(int x) {
+ char foo[10];
+ int bar[20];
+ char qux[30];
+
+ (void)sizeof(bar + 10); // expected-warning{{sizeof on pointer operation will return size of 'int *' instead of 'int [20]'}}
+ (void)sizeof(foo - 20); // expected-warning{{sizeof on pointer operation will return size of 'char *' instead of 'char [10]'}}
+ (void)sizeof(bar - x); // expected-warning{{sizeof on pointer operation will return size of 'int *' instead of 'int [20]'}}
+ (void)sizeof(foo + x); // expected-warning{{sizeof on pointer operation will return size of 'char *' instead of 'char [10]'}}
+
+ // This is ptrdiff_t.
+ (void)sizeof(foo - qux); // no-warning
+
+ (void)sizeof(foo, x); // no-warning
+ (void)sizeof(x, foo); // expected-warning{{sizeof on pointer operation will return size of 'char *' instead of 'char [10]'}}
+}