Dave Bryan wrote:
Dear ListFolks,
I am unable to set breakpoints, and therefore unable to debug, GPC programs under GDB. The cause appears to be bad debugging information generated by GPC. For example, compiling:
program debug (output);
var i, j: integer;begin i := 1; j := 2; writeln ('A Pascal test'); writeln ('Variable i is ', i); writeln ('Variable j is ', j) end.
with:
gpc -g -o debug.exe debug.pas
and starting GDB with:
gdb debug.exe
and then trying to set breakpoints, I see the following:
(gdb) break 6 Breakpoint 1 at $4011f2: file <implicit code>, line 6. (gdb) break 8 Note: breakpoint 1 also set at pc $4011f2. Breakpoint 2 at $4011f2: file <implicit code>, line 8. (gdb) break 10 Note: breakpoints 1 and 2 also set at pc $4011f2. Breakpoint 3 at $4011f2: file <implicit code>, line 10.
The following method works here:
Set a breakpoint on "pascal_main_program", run it, and when it stops at the breakpoint (which is the first line of your main program body), set all other breakpoints you need (and delete the first one, if you like to). This step is needed just once, i.e. even if your program terminates, you may set any breakpoints normally and rerun it, without the hack just described.
Example:
(gdb) break pascal_main_program Breakpoint 1 at $8049bc6: file test.pas, line 6. (gdb) run Starting program: /mnt/sda2/home/ejer5183/pascal/a.out
Breakpoint 1, pascal_main_program () at test.pas:6 6 i := 1; (gdb) delete 1 (gdb) break 6 Breakpoint 2 at $8049bc6: file test.pas, line 6. (gdb) break 8 Breakpoint 3 at $8049bda: file test.pas, line 8. (gdb) cont Continuing.
Breakpoint 3, pascal_main_program () at test.pas:8 8 writeln ('A Pascal test'); (gdb) Continuing. A Pascal test Variable i is 1 Variable j is 2
Program exited normally. (gdb) break 10 Breakpoint 4 at $8049c50: file test.pas, line 10. (gdb) delete 2 (gdb) delete 3 (gdb) run Starting program: /mnt/sda2/home/ejer5183/pascal/a.out A Pascal test Variable i is 1
Breakpoint 4, pascal_main_program () at test.pas:10 10 writeln ('Variable j is ', j) (gdb)
Emil Jerabek
Note that all breakpoints reference the same address. Attempting to start the program gives:
(gdb) r Starting program: D:/debug.exe
Breakpoint 1, init_pascal_main_program () at <implicit code>:11 11 <implicit code>: No such file or directory. in <implicit code>
If I try running "objdump", I see the following:
objdump --debugging debug.exe
debug.exe: file format pei-i386
Bad stab: Datevalid:(0,21)=@s8;16;,0,8;Timevalid:(0,21),8,8; Year:(0,1),32,32;Month:(0,22)=r(0,1);0000000000001;0000000000014;,64,32; Day:(0,23)=r(0,1);0000000000001;0000000000037;,96,32; Dayofweek:(0,24)=r(0,1);0000000000000;0000000000006;,128,32; [...]
Running "objdump" on the object file yields a similar error report.
I've reproduced this on several PCs, as follows:
OS: Win95, WinNT4, Win2K
GPC versions: 20011222 (i486-pc-mingw32msvc, 2.95.3) 20020318 (i386-unknown-mingw32 -- the Chief's distro) 20020410 (i486-pc-mingw32msvc, 2.95.3) 20020410 (i686-pc-cygwin, 2.95.3)
GDB versions: 4.18, 5.0, 5.1.1
Is this the same error that is listed in the "Known Bugs" section of the GPC manual as:
"...error in debug entries generated for objects" 8F990E3D9A6FD1118F3B0000F81EA1D84985D7@exchsa2.dsto.defence.gov.au
-- Dave Bryan