Programming

It failed to show the values of some variables. but actually these are general-sense varialbes. They should be in current context and alsolutely not in comments.

After the execution of the related statements, those variables are changed and can be used in the continuing code.

Please teach me. Thanks

Samples:

(gdb) p *ghy->tee-tree
No symbol "ghy" in current context.
(gdb)
224
(gdb) p rand
$3 = {<text variable, no debug info>} 0x3aebe33ce0 <rand>
(gdb) p *rand
$4 = {<text variable, no debug info>} 0x3aebe33ce0 <rand>

A similer sample: what does it mean using 'value optimized out'?

<value optimized out>

"Value optimized out" is when the compiler assumes a value is constant and starts hardcoding it instead of reading it from memory. For example:

Code:

int main(void)
{
  int x=5, y=1, z;
  for(z=0; z<10; z++)
  {
    y=y+x;
  }
}

The compiler can see that nothing else ever assigns a value to x, and if told to optimize the code, will assume it to be a constant value. Knowing this, the compiler may create code like ADD $Y, 5 instead of ADD $Y, $X which has the advantage of not needing to read the value of X from memory every loop.

Having gone this far it may decide that there's no reason for x to actually exist at all, and remove it. Hence value optimized out. Even if it does leave it around you may be in for a suprise when you poke in changes with your debugger; this hardcoded optimization would ignore it.

So it may be that trying to debug an optimized executable is causing all this missingness. Try recompiling with -O0 and see if anything comes back.