I've tried hooking to other commands such as echo and it works well. But when it comes to hooking the x command, it fails. Here's the codes inside of my .gdbinit file.
set $pince_injection_failed = 1
set $pince_debugging_mode = 0
define hook-x
if $pince_injection_failed = 1
echo asdf
end
define hookpost-x
if $pince_debugging_mode = 0
echo zxcv
end
I'm aware that gdb doesn't accept aliases of a function for hooking. But x is already a full function isn't it? I couldn't find any aliases for it. I'm also doubting about it because a single character is too short for a command to be
I found the solution thanks to the Mark Plotnick. It seems like another fault of mine, I found out that there was a function that had a misplaced end, so all functions came after that function got ignored by gdb naturally.
define keks
set $lel=0
while($lel<10)
x/x 0x00400000
set $lel = $lel+1
end
Notice the missing end at the end of while loop
Related
TL;DR
How to find where exactly vim or nvim error started (which file?) when I'm interested in fixing the actual issue and not just removing the bad plugin? Anything better than strace and guesswork to find the error origin?
Issue
I often add a plugin to my vim or nvim config and end up getting errors on hooks (buffer open, close, write):
"test.py" [New] 0L, 0C written
Error detected while processing function 343[12]..272:
line 8:
E716: Key not present in Dictionary: _exec
E116: Invalid arguments for function get(a:args, 'exec', a:1['_exec'])
E15: Invalid expression: get(a:args, 'exec', a:1['_exec'])
The problem is, I have no idea where those come from, only get some line number of unknown file and I know it's not my vim/nvim config file.
Somewhere, you have a plugin that has defined a dictionary with anonymous-functions (check the help related to this tag).
For the curious ones, it's done this way:
let d = {}
function! d.whatever() abort
throw "blah"
endfunction
When you execute this function, you'll get the kind of error you're currently observing. That's why I stopped working this way to prefer:
let d = {}
function s:whatever() abort
throw "blah"
endfunction
let d.whatever = function('s:whatever') " a workaround is required for older versions of vim
" At least this way I'll get a `<SNR>42_whatever` in the exception throwpoint, and thus a scriptname.
That's the why. Now, back to your problem, AFAIK, the only things you'll be able to know are the two functions that have been called:
in line 12 of :function {343}, you've called
:function {272} which contains an error at line 8.
Thanks to these two commands (may be prefixed with :verbose, I don't remember exactly), you'll get the source code of the two functions, which you should be able to use in order to grep your plugins to know where it appears.
I am trying to debug a C++ program using GDB. I have set 15 breakpoints. Most of the breakpoints are in different files. After the first 5 breakpoints, it became difficult to remember what line of code any given breakpoint refers to.
I struggle quite a bit simply trying to recall what a given breakpoint refers to. I find this quite distracting. I was wondering if there is a way to tell gdb to display code around a certain breakpoint.
Something like this - $(gdb) code 3 shows 30 lines of code around breakpoint 3. Is this possible today. Could you please show me how?
I run gdb in tui mode, and I also keep emacs open to edit my source files.
You can use gdb within emacs.
In emacs, type M-x gdb, after entering the name of the executable, type M-x gdb-many-windows. It brings up an IDE-like interface, with access to debugger, locals, source, input/output, stack frame and breakpoints.
You can find a reference and snapshot here.
I don't think you can do it exactly like this in gdb as such, but it can be scripted in gdb python.
This crude script should help:
import gdb
class Listbreak (gdb.Command):
""" listbreak n Lists code around breakpoint """
def __init__ (self):
super(Listbreak, self).__init__ ("listbreak", gdb.COMMAND_DATA)
def invoke (self, arg, from_tty):
printed = 0
for bp in gdb.breakpoints():
if bp.number == int(arg[0]):
printed = 1
print ("Code around breakpoint " + arg[0] + " (" + bp.location + "):")
gdb.execute("list " + bp.location)
if printed == 0:
print ("No such breakpoint")
Listbreak()
Copy this to listbreak.py, source it in gdb (source listbreak.py), then use it like this:
listbreak 2
I'm trying to setup a set of functions to be skipped by gdb from stepping in by commands like:
skip myfunction
. But if I place them in ~/.gdbinit instead of just saying in the terminal gdb prompt, I get the error:
No function found named myfunction.
Ignore function pending future shared library load? (y or [n]) [answered N; input not from terminal]
So I need GDB to get Y answer. I've tried what was suggested for breakpoints as well as set confirm off suggested in a comment to this question. But these don't help with skip command.
How can I set skip in a .gdbinit script, answering Y about future library load?
you can use Python to wait for the execution to start, which is equivalent to pending on:
import gdb
to_skip = []
def try_pending_skips(evt=None):
for skip in list(to_skip): # make a copy for safe remove
try:
# test if the function (aka symbol is defined)
symb, _ = gdb.lookup_symbol(skip)
if not symb:
continue
except gdb.error:
# no frame ?
continue
# yes, we can skip it
gdb.execute("skip {}".format(skip))
to_skip.remove(skip)
if not to_skip:
# no more functions to skip
try:
gdb.events.new_objfile.disconnect(try_pending_skips) # event fired when the binary is loaded
except ValueError:
pass # was not connected
class cmd_pending_skip(gdb.Command):
self = None
def __init__ (self):
gdb.Command.__init__(self, "pending_skip", gdb.COMMAND_OBSCURE)
def invoke (self, args, from_tty):
global to_skip
if not args:
if not to_skip:
print("No pending skip.")
else:
print("Pending skips:")
for skip in to_skip:
print("\t{}".format(skip))
return
new_skips = args.split()
to_skip += new_skips
for skip in new_skips:
print("Pending skip for function '{}' registered.".format(skip))
try:
gdb.events.new_objfile.disconnect(try_pending_skips)
except ValueError: pass # was not connected
# new_objfile event fired when the binary and libraries are loaded in memory
gdb.events.new_objfile.connect(try_pending_skips)
# try right away, just in case
try_pending_skips()
cmd_pending_skip()
Save this code into a Python file pending_skip.py (or surrounded with python ... end in your .gdbinit), then:
source pending_skip.py
pending_skip fct1
pending_skip fct2 fct3
pending_skip # to list pending skips
Documentation references:
GDB Python TOC
Basic Python
Events in Python
Symbols in Python
This feature has been proposed here:
https://sourceware.org/ml/gdb-prs/2015-q2/msg00417.html
https://sourceware.org/bugzilla/show_bug.cgi?id=18531
So far, there's been no activity on that issue for 6 months though. As of writing this, the feature is not included in GDB 7.10.
I have a Fortran program that starts with opening and reading data from a .txt file.
At the end of the program a new file is written, which replaces the old file (that was originally imported).
However it can occur that the file that needs to be opened does not exists, for that case the variables that should be imported from the .txt file should be 0.
I thought by doing this with the code below, however this does not work and the script is aborted when the file history.txt does not exists.
How can I let the script set default values to my variables when the history.txt file does not exists?
OPEN(UNIT=in_his,FILE="C:\temp\history.txt",ACTION="read")
if (stat .ne. 0) then !In case history.txt cannot be opened (iteration 1)
write(*,*) "history.txt cannot be opened"
KAPPAI=0
KAPPASH=0
go to 99
end if
read (in_his, *) a, b
KAPPAI=a
KAPPASH=b
write (*, *) "KAPPAI=", a, "KAPPASH=", b
99 close(in_his)
The file that is imported is pretty simple and looks like:
9.900000000000006E-003 3.960000000000003E-003
I would use IOSTAT as stated by #Fortranner. I would also set defaults before trying to open the file and I tend not to use goto's. As in:
program test
implicit none
integer :: in_his, stat
real :: KAPPAI, KAPPASH
in_his = 7
KAPPAI = 0
KAPPASH = 0
OPEN(UNIT=in_his, FILE="history.txt",ACTION='read',IOSTAT=stat,STATUS='OLD')
if (stat .ne. 0) then
write(*,*) "history.txt cannot be opened"
stop 1
end if
read (in_his, *) KAPPAI, KAPPASH
close(in_his)
write (*, *) "KAPPAI=", KAPPAI, "KAPPASH=", KAPPASH
end program test
Another way is to use an inquire statement and check for the existence of the file before you try to open it. This would set a logical variable that could be used in an IF statement to handle the two cases: 1) open file and read values, or 2) set default values w/o opening the file. Or set the default values first, then have the IF statement only handle the case of opening the file and reading the values.
Set iostat in the open statement and handle the case where it is nonzero.
There are two ways to do this. One is using IOSTAT specifier in the OPEN statement like Fortranner and Timothy Brown suggested. The other is to use the ERR specifier in the OPEN statement which lets you specify a label to which the program will transfer control in the even of an error:
OPEN(UNIT=in_his,FILE="C:\temp\history.txt",ACTION="read",STATUS='OLD',ERR=101)
...
101 CONTINUE
The label must be in the same scoping unit as the OPEN statement.
I am writing a code in Fortran to read a list of properties from a file, and am using the IOSTAT function to skip invalid data. The relevant section of code is as follows:
do j=1,1000
read(22,*,IOSTAT=ios) step,T,K,U,Tot,P
If(IS_IOSTAT_END(ios)) Exit !exits loop if value is not number or end of file
IF(ios.ne.0) cycle
sumT=sumT+T
sumU=sumU+U
sumK = sumK + K
sumKsq = sumKsq + (K**2.d0)
end if
end do
This code has previously worked fine when running on Linux, but when running on Mac OSX I get the error message 'IS_IOSTAT_END has no implicit type'. Could somebody please explain how to correct this?
Thanks
The intrinsic procedure IS_IOSTAT_END(i) is defined since Fortran 2003. Sufficiently recent compiler version must be used.