[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
https://github.com/jasonmolenda closed https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
https://github.com/bulbazord approved this pull request. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
@@ -3154,7 +3154,7 @@ AppleObjCRuntimeV2::TaggedPointerVendorExtended::GetClassDescriptor( << m_objc_debug_taggedpointer_ext_payload_lshift) >> m_objc_debug_taggedpointer_ext_payload_rshift); int64_t data_payload_signed = - ((int64_t)((int64_t)unobfuscated + ((int64_t)((uint64_t)unobfuscated << m_objc_debug_taggedpointer_ext_payload_lshift) >> bulbazord wrote: Makes sense to me. I think this is fine then. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
https://github.com/jasonmolenda edited https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
@@ -3154,7 +3154,7 @@ AppleObjCRuntimeV2::TaggedPointerVendorExtended::GetClassDescriptor( << m_objc_debug_taggedpointer_ext_payload_lshift) >> m_objc_debug_taggedpointer_ext_payload_rshift); int64_t data_payload_signed = - ((int64_t)((int64_t)unobfuscated + ((int64_t)((uint64_t)unobfuscated << m_objc_debug_taggedpointer_ext_payload_lshift) >> jasonmolenda wrote: e.g. ``` (lldb) p (-5LL <<60) >> 60 (long long) -5 ``` if the bit slice we're pulling out has its high bit set, that'll shfit down and be sign extended. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
@@ -3154,7 +3154,7 @@ AppleObjCRuntimeV2::TaggedPointerVendorExtended::GetClassDescriptor( << m_objc_debug_taggedpointer_ext_payload_lshift) >> m_objc_debug_taggedpointer_ext_payload_rshift); int64_t data_payload_signed = - ((int64_t)((int64_t)unobfuscated + ((int64_t)((uint64_t)unobfuscated << m_objc_debug_taggedpointer_ext_payload_lshift) >> jasonmolenda wrote: Probably the one interesting thing is that the value we're slicing out is, apparently, signed, so we want it to sign extend to Int64 when it is done. That would take a little more care with a bit slice approach. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
@@ -3154,7 +3154,7 @@ AppleObjCRuntimeV2::TaggedPointerVendorExtended::GetClassDescriptor( << m_objc_debug_taggedpointer_ext_payload_lshift) >> m_objc_debug_taggedpointer_ext_payload_rshift); int64_t data_payload_signed = - ((int64_t)((int64_t)unobfuscated + ((int64_t)((uint64_t)unobfuscated << m_objc_debug_taggedpointer_ext_payload_lshift) >> jasonmolenda wrote: I suspect the runtime gave us these "left & right shift" values, and the person who wrote this used the obvious implementation. It could be expressed as a bit slice with a little subtraction, true. Just to be clear, we're not fixing a real bug here, we were saying a UInt64 was signed and then ubsan got all shirty when we shifted away some bits that would indicate sign. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
@@ -3154,7 +3154,7 @@ AppleObjCRuntimeV2::TaggedPointerVendorExtended::GetClassDescriptor( << m_objc_debug_taggedpointer_ext_payload_lshift) >> m_objc_debug_taggedpointer_ext_payload_rshift); int64_t data_payload_signed = - ((int64_t)((int64_t)unobfuscated + ((int64_t)((uint64_t)unobfuscated << m_objc_debug_taggedpointer_ext_payload_lshift) >> clayborg wrote: We could just shift right and then mask. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
@@ -3154,7 +3154,7 @@ AppleObjCRuntimeV2::TaggedPointerVendorExtended::GetClassDescriptor( << m_objc_debug_taggedpointer_ext_payload_lshift) >> m_objc_debug_taggedpointer_ext_payload_rshift); int64_t data_payload_signed = - ((int64_t)((int64_t)unobfuscated + ((int64_t)((uint64_t)unobfuscated << m_objc_debug_taggedpointer_ext_payload_lshift) >> bulbazord wrote: Since the goal is to extract some bits from the middle of this 64-bit value, is there a way we could produce a mask instead of shifting left and then shifting right? https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
[Lldb-commits] [lldb] [lldb] [ObjC runtime] Don't cast to signed when left shifting (PR #86605)
jasonmolenda wrote: I've seen this ubsan error every time I run the testsuite for years, i just finally sat down and figured out what was going on. https://github.com/llvm/llvm-project/pull/86605 ___ lldb-commits mailing list lldb-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-commits
