Re: [Tinycc-devel] Debugger options: difference output between linux and windows

[Michael Matz]

Hello,

On Fri, 15 May 2020, Massimo Sala wrote:

> * linux:   -DLUA_USE_LINUX -g -b
>    lua -v
>    bcheck.c __bound_ptr_add: 0x7fffffffe66f is outside of the region
>    bcheck.c bound_error: invalid pointer
>    /opt/packages/tcc.sh: line 49: 19914 Segmentation fault      ./lua -v
>
> From the output I cannot understand if this instrumentation is working and
> there is a problem in Lua, or there is a problem in the tcc instrumentation
> code.
>
> I read at https://bellard.org/tcc/tcc-doc.html    "Note: -b is only
> available on i386"
> Does it mean cannot work on intel, 64 bits cpu ?

Nope, that's outdated docu, -b is supposed to work on x86-64.  But I fear 
you'll have to debug this a bit on your own.  Current mob branch should 
actually be a bit more verbose in telling where the invalid access is 
happening, so it seems you're using an older version; please update to 
current git.

In the worst case you can run the whole thing in a debugger and set a 
breakpoint on bound_error or tcc_backtrace.  In recent mob branch you can 
also set the environment variable TCC_BOUNDS_NEVER_FATAL to 1, in which 
case the error is only logged but the program keeps running (and possibly 
accessing the invalid pointer, which might turn out to be harmless).


Ciao,
Michael.