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Trailing-Edge - PDP-10 Archives - bb-bt99e-bb - alg10b.d06
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                 EDIT DESCRIPTIONS FOR ALGOL-10-V10B                            
  
  
                             EDIT 341    FOR ALGOL
  
  
  
  
[SYMPTOM]
  
Strings can write over each other,  corrupting  memory  and  the  heap
table  after  a  multiple-parameter  READ  is  done  with EOF trapping
enabled.
  
  
[DIAGNOSIS]
  
ALGLIB procedure READ improperly zeroes the "heap space in use"  flag.
It should be cleared after each parameter is read, not after the whole
READ call has completed.
  
  
[CURE]
  
Clear the "heap space in use" flag immediately before looping to  read
more parameters, not after.
********************************************************************************
  
  
                             EDIT 342    FOR ALGOL
  
  
  
  
[SYMPTOM]
  
Edit 332 causes  various  problems  such  as  fixed  point  overflows,
illegal memory references, etc., in ALGDDT.
  
  
[DIAGNOSIS]
  
Edit 332 delocated register AX before preserving it during  an  ALGDDT
breakpoint.   However,  if  the  register contained data rather than a
relocated address, an APR trap  would  be  generated  in  some  cases,
depending on the contents of AX.
  
  
[CURE]
  
Do not delocate or relocate AX when preserving it in a breakpoint.
********************************************************************************
  
  
  
END OF  ALGOL-10-V10B