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

On 25 Apr 2002, at 18:30, Emil Jerabek wrote:

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....

Indeed, that works fine. Thanks for the workaround.

-- Dave Bryan