• Scott Mayo <Scott_member pathlink.com> Mar 17 2006
• Heinz Saathoff <newshsaat arcor.de> Mar 20 2006
• Scott Mayo <Scott_member pathlink.com> Mar 20 2006

My first day using dmc. I fed it some C++ code that was known to be
well-behaved; the resulting .exe crashed. I couldn't get the assembler listing
working, but I was able to move code and get the correct behaviour.  

The crashing code:

switch (p->cmd) //dies around here
{
case CMD_Set:
setpins(p->pinset, p->set.onV);
return 0;

case CMD_SetFreq:
for (i = 0; i < 5; ++i)
..etc


The working code, which is equivalent:

//DigitalMars compiler generates a jump to address 0
//if this is a case in the switch
//no problem as an If, though.
#if 01
if (p->cmd == CMD_Set)
{
setpins(p->pinset, p->set.onV);
return 0;
}
#endif

switch (p->cmd)
{
case CMD_Set:
setpins(p->pinset, p->set.onV);
return 0;

case CMD_SetFreq:
for (i = 0; i < 5; ++i)


I'm new here - does anyone do support? I can make the source available; the
compile command line was just 
dmc mycode.cpp

The code uses no explicit new/delete/malloc/stl/iostreams/overloading or any
interesting trickery. There is some inline asembler, but when I compile and run
it as a console app using the microsoft IDE, that same assmbler runs just fine,
so I don't think it's doing any damage. Really looks like a compiler issue to
me. Help?

Another trick that worked, then the code was part of the switch statement, was
to put a fprintf in the case. 

Hello,

Scott Mayo wrote...
 My first day using dmc. I fed it some C++ code that was known to be
 well-behaved; the resulting .exe crashed. I couldn't get the assembler listing
 working, but I was able to move code and get the correct behaviour.  
 
 The crashing code:
 
 switch (p->cmd) //dies around here
 {
 case CMD_Set:
 setpins(p->pinset, p->set.onV);
 return 0;
 
 case CMD_SetFreq:
 for (i = 0; i < 5; ++i)
 ..etc



Mybe an uninitialized pointer p? What makes me think it's this kind of 
error is that your code works when adding the extra statements. I know 
that adding/deleting portions of code can influence the data arrangement 
on the stack and make uninitialized pointers crash/not crash the 
program.


- Heinz

Mybe an uninitialized pointer p? What makes me think it's this kind of 
error is that your code works when adding the extra statements. 


No, but it was my error - I went off the end of an array and clobbered the first
entry of the switch jump table. The compiler is not to blame.