I was trying to look at e content of dyn-arrays under gdb and found that it is very hard to get results.
(you may also want to look at
http://www.lazarus.freepascal.org/index.php?name=PNphpBB2&file=viewtopic&t=4763
)
I used ptype to look at what gdb (under Lazarus) thinks the variable is. declaring the following in my source (same for word/integer/...):
type
Tab = array of byte;
var
ab : Tab;
ab2 : array of byte;
b1 : ^tab;in "gbb -i mi"
ptype ab
type = array [0..-1] of BYTE
ptype @ab\n"
type = ^BYTE
ptype ab2
type = array [0..-1] of BYTE
ptype @ab2
type = ^(array [0..-1] of BYTE)
ptype b1
type = ^BYTE
I would assume that the type info is included by fpc?
IMHO it is inconsistent, and partly incorrect. So I am looking for any feedback, maybe I got something wrong, maybe it is a bug, maybe there is an intention?
-inconsistent: ab and ab2 are the same type to the debugger, yet @ab and @ab2 return different
-incorrect: ab and ab2 are "array [] of byte", but in reality they are pointers.
As a result "-data-evaluate-expression ab[0]" does return the wrong value (It contains a byte out of the address of ab)
I don't know what the correct values should be, and despite the debugger returning a ptype of "^{array [0..-1] of BYTE"; I don't know if that can be set.
In terms of data evaluation, if ^(array...) is not possible (or does not work in gdb?) then ^BYTE would probably be the best choice? Forcing b1 to point to the array ("b1=@(ab[0]"), and not to it's address ("") allows to do b1^[x] and get the correct data.
I don't expect there is a way to have ptype return the pascal declaraton (which hdes the fact about the pointer), yet have gdb knowing of the pointer?
Regards
Martin