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Conference azur::mcc

Title:DECmcc user notes file. Does not replace IPMT.
Notice:Use IPMT for problems. Newsletter location in note 6187
Moderator:TAEC::BEROUD
Created:Mon Aug 21 1989
Last Modified:Wed Jun 04 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:6497
Total number of notes:27359

2167.0. "Certain MCC Typedefs Can Cause Nasty Stack Problems" by TOOK::SWIST (Jim Swist LKG2-2/T2 DTN 226-7102) Wed Jan 22 1992 13:03

    Warning to MM Developers - 
    
    The typedefs in mcc_interface_def.h for MCC data types
    MCC_T_Latin1String, MCC_T_OctetString, MCC_T_HexString, and
    MCC_T_Expression are defined in terms of their maximum length, namely
    "char[65535]".  Such types are useful as pointers only since it is
    unlikely you really want a variable of that length allocated.
    
    We have had several cases of *very* hard to debug memory clobbers
    caused by attempting to put one of the above types on the stack as a
    local variable.  This caused the thread stack to overflow by so much
    that the protected guard pages at the bottom of the stack were in fact
    jumped over and random memory was clobbered.
    
    In V1.2, the guard band size will be adjustable to help find stuff like
    this, but in the meantime caveat coder.
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