[Rd] Trouble debugging with gdb, R on Windows

Duncan Murdoch murdoch at stats.uwo.ca
Fri Mar 18 20:59:56 CET 2005

On Fri, 18 Mar 2005 09:49:28 -0800, Seth Falcon <sfalcon at fhcrc.org>
wrote :

>I'm trying to follow the example in the R for Windows FAQ on running
>gdb and am getting stuck because gdb tells me "Cannot access memory at
>address ...".
>Here's what my gdb session looks like (This one from a cygwin shell,
>but same results from plain Windows CMD shell):
>$ cd R-devel/src/gnuwin32
>$ gdb ../../bin/Rgui.exe
>GNU gdb 5.2.1
>Copyright 2002 Free Software Foundation, Inc.
>GDB is free software, covered by the GNU General Public License, and you are
>welcome to change it and/or distribute copies of it under certain conditions.
>Type "show copying" to see the conditions.
>There is absolutely no warranty for GDB.  Type "show warranty" for details.
>This GDB was configured as "i686-pc-mingw32"...

I'm using the same version as you, but I don't see what you're seeing.
You got

>(gdb) break WinMain
>Breakpoint 1 at 0x401296: file ../graphapp/graphappmain.c, line 59.
>(gdb) run
>Starting program: y:\falcon\src\R-devel\src\gnuwin32/../../bin/Rgui.exe
>Breakpoint 1, WinMain (Instance=0x400000, PrevInstance=0x0,
>    CmdLine=0x261f26 "", CmdShow=10) at ../graphapp/graphappmain.c:59
>59              startgraphapp(Instance, PrevInstance, CmdShow);
>(gdb) break R_ReadConsole
>Cannot access memory at address 0x23e17
>(gdb) info symbol 0x23e17
>R_ReadConsole in section .text

and I get

(gdb) b WinMain
Breakpoint 1 at 0x401296: file ../graphapp/graphappmain.c, line 59.
(gdb) run
Starting program: f:\R\svn\r-devel\R\src\gnuwin32/../../bin/Rgui.exe

Breakpoint 1, WinMain (Instance=0x400000, PrevInstance=0x0,
    CmdLine=0x251f13 "", CmdShow=10) at ../graphapp/graphappmain.c:59
59              startgraphapp(Instance, PrevInstance, CmdShow);
(gdb) break R_ReadConsole
Breakpoint 2 at 0x1001d5e6
(gdb) info symbol 0x1001d5e6
R_ReadConsole + 6 in section .text

The only thing I can see is that your address for R_ReadConsole looks
suspiciously low:  normally code gets loaded at addresses above
0x400000.  I have no idea what would cause this, and am not even sure
it's not perfectly reasonable.

A workaround that might help would be to use the R menu item
"Misc|Break to debugger" to break out of R once it is running, and set
your breakpoints then, but I don't know that it will make any

Duncan Murdoch

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