[libunwind] Undefined behaviour pointer arithmetic with null pointer (#98648)

DanielKristofKiss · web-flow · commit 710590e33d19 · 2024-08-05T11:16:51.000+02:00
Fixes #91144
diff --git a/libunwind/src/UnwindCursor.hpp b/libunwind/src/UnwindCursor.hpp
@@ -230,8 +230,8 @@ void DwarfFDECache<A>::iterateCacheEntries(void (*func)(
 }
 #endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)
 
-
-#define arrayoffsetof(type, index, field) ((size_t)(&((type *)0)[index].field))
+#define arrayoffsetof(type, index, field)                                      \
+  (sizeof(type) * (index) + offsetof(type, field))
 
 #if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)
 template <typename A> class UnwindSectionHeader {

Original file line number	Diff line number	Diff line change
`@@ -230,8 +230,8 @@ void DwarfFDECache<A>::iterateCacheEntries(void (*func)(`
`230`	`230`	`}`
`231`	`231`	`#endif // defined(_LIBUNWIND_SUPPORT_DWARF_UNWIND)`
`232`	`232`
`233`		`-`
`234`		`-#define arrayoffsetof(type, index, field) ((size_t)(&((type *)0)[index].field))`
	`233`	`+#define arrayoffsetof(type, index, field) \`
	`234`	`+ (sizeof(type) * (index) + offsetof(type, field))`
`235`	`235`
`236`	`236`	`#if defined(_LIBUNWIND_SUPPORT_COMPACT_UNWIND)`
`237`	`237`	`template <typename A> class UnwindSectionHeader {`