Hi David,
David Chisnall wrote:
On 18 Jun 2020, at 12:52, Riccardo Mottola <riccardo.mott...@libero.it> wrote:
you guessed correctly and the protocol is also a very common one, NSCopying
So, part of the question is whether this is the first time we’re seeing this or
not. Can you stick a watchpoint on the isa pointer and restart it, see if it’s
modified before here?
as simple as this?
(gdb) watch aProto->isa
Hardware watchpoint 4: aProto->isa
I rerun the program but it fails through to the crash - so it appears
that it does not het changed, or I did not set it correct.
That’s very odd. Here’s the definition of the enum:
https://github.com/gnustep/libobjc2/blob/369c84db35a6a1e94f8a4689a695fabdac056166/protocol.h#L26
The isa pointer for each protocol is initially set to one of those enum values
(2, 3, or 4) by the compiler and is then set to a proper Objective-C class. It
should never end up 0. It’s possible that something has corrupted memory or
that we’ve just read the low 32 bits this has been set to a 64-bit address that
happens to have nothing in the low 32 bits, but it seems quite unlikely.
I see, this is very strange. What is "really" strange is that that this
is amd64 bit architecture and a known compiler, the same code works on
FreeBSD (and Linux IIRC).
NetBSD would make the difference? or that this is "genuine AMD" and not
intel? would be very strange.
I confirm OLDABI_COMPAT is on. I did not touch it. LEGACY_COMPAT is off.
I only changed the linker option and then the build type.
Further question: this is a from-scratch install, all compiled with the same
version of clang, can I assume that all libraryes have the same ABI or not?
maybe there is a makefile issue somewhere?
Should be. You can see if __objc_exec_class is called - that’s the entry point
used by old ABI code.
(gdb) b __obj_exec_class
Function "__obj_exec_class" not defined.
Apparently it is not even defined, but this is strange, since I compiled
with OLDABI_COMPAT:
I tried being more explicit:
(gdb) b loader.c:328
Breakpoint 3 at 0x72b92fe1859f: file
/home/multix/code/gnustep-vcs/libobjc2/loader.c, line 330.
and re-run the program, it does not get into that function, so we can
assume it is new code.
Riccardo
