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authorPatric Stout <truebrain@openttd.org>2020-12-04 22:12:39 +0100
committerPatric Stout <github@truebrain.nl>2020-12-06 16:10:58 +0100
commitc98717cb4518d80ccccb2ae1677d0a394542f129 (patch)
treea1c585edd2b1fa672de3fb4e88be8f8efb08f6c1
parentc558936ec3223f95677e182da1325717f8163ef6 (diff)
downloadopenttd-c98717cb4518d80ccccb2ae1677d0a394542f129.tar.xz
Fix: do not add an offset to a nullptr
This is, by specs, undefined behaviour. See https://reviews.llvm.org/D67122 In cases where this is done, optimizations done by LLVM can generate code that causes crashes. GetVariableAddress() had two (legit) ways this could happen: - For SaveLoad set to global - For SaveLoad set to SLE_VAR_NULL, where sld->address is always a nullptr, and object could or could not be a nullptr.
-rw-r--r--src/saveload/saveload.h13
1 files changed, 12 insertions, 1 deletions
diff --git a/src/saveload/saveload.h b/src/saveload/saveload.h
index abd58ea04..3581a5594 100644
--- a/src/saveload/saveload.h
+++ b/src/saveload/saveload.h
@@ -873,7 +873,18 @@ static inline bool IsNumericType(VarType conv)
*/
static inline void *GetVariableAddress(const void *object, const SaveLoad *sld)
{
- return const_cast<byte *>((const byte*)(sld->global ? nullptr : object) + (ptrdiff_t)sld->address);
+ /* Entry is a global address. */
+ if (sld->global) return sld->address;
+
+ /* Entry is a null-variable, mostly used to read old savegames etc. */
+ if (GetVarMemType(sld->conv) == SLE_VAR_NULL) {
+ assert(sld->address == nullptr);
+ return nullptr;
+ }
+
+ /* Everything else should be a non-null pointer. */
+ assert(object != nullptr);
+ return const_cast<byte *>((const byte *)object + (ptrdiff_t)sld->address);
}
int64 ReadValue(const void *ptr, VarType conv);