[fpc-devel] Possible internal corruption

J. Gareth Moreton gareth at moreton-family.com
Fri Jun 29 13:09:18 CEST 2018

 So I've made a breakthrough. The memory corruption is due to both parts of
the CMOV optimization under OptPass2Jcc, not my Jcc addition (although it
might have unintentionally accentuated it). The first part sets p to a
dangling pointer, while the 2nd part is a little more complicated, but I'll
try to spell everything out once I finish testing my new patch and see if
I've eliminated all of my crashes


 On Fri 29/06/18 10:05 , "J. Gareth Moreton" gareth at moreton-family.com
  It turns out that it's invalid memory.  Trying to call "ClassName"
raises an access violation (other aligns work fine).  There's a dangling
pointer somewhere.  I found one in the CMOV optimisation code, but that
hasn't fixed the crash.


 On Fri 29/06/18 10:27 , Martok listbox at martoks-place.de sent:
 > A clue that leads me to believe there's internal corruption is that a
 > .s file yields an alignment field of ".balign 119,0x90", which should
 > happen. 
 Could you set a breakpoint on aggas.pas:721 (the call to doalign) with a 
 conditional on "tai_align_abstract(hp).aligntype=119" and check what the
 type of hp is? It could be that at some point a node gets its typ changed
in an 
 invalid way? 
 aligntype should be either one of 2^[0..5], never something else... 

 This is where AddressSanitizer support would be *nice*. 


 Ceterum censeo b32079 esse sanandam. 

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