I have some C++ code like this that I'm stepping through with GDB:
void foo(int num) { ... }
void main() {
Baz baz;
foo (baz.get());
}
When I'm in main(), I want to step into foo(), but I want to step over baz.get().
The GDB docs say that "the step command only enters a function if there is line number information for the function", so I'd be happy if I could remove the line number information for baz.get() from my executable. But ideally, I'd be able to tell GDB "never step into any function in the Baz class".
Does anyone know how to do this?
Starting with GDB 7.4, skip can be used.
Run info skip, or check out the manual for details: https://sourceware.org/gdb/onlinedocs/gdb/Skipping-Over-Functions-and-Files.html
Instead of choosing to "step", you can use the "until" command to usually behave in the way that you desire:
(gdb) until foo
I don't know of any way to permanently configure gdb to skip certain symbols (aside from eliding their debugging information).
Edit: actually, the GDB documentation states that you can't use until to jump to locations that aren't in the same frame. I don't think this is true, but in the event that it is, you can use advance for the same purpose:
(gdb) advance foo
Page 85 of the GDB manual defines what can be used as "location" arguments for commands that take them. Just putting "foo" will make it look for a function named foo, so as long as it can find it, you should be fine. Alternatively you're stuck typing things like the filename:linenum for foo, in which case you might just be better off setting a breakpoint on foo and using continue to advance to it.
(I think this might be better suited as a comment rather than an answer, but I don't have enough reputation to add a comment yet.)
So I've also been wanting to ignore STL, Boost, et al (collectively '3rd Party') files when debugging for a while. Yesterday I finally decided to look for a solution and it seems the nearest capability is the 'skip' command in GDB.
I found the 'skip' ability in GDB to be helpful, but it's still a nuisance for me because my program uses a lot of STL and other "3rd Party" template code. In this case I have to mark a bunch of files as skip. After the 2nd time doing so I realized it would be more helpful to be able to skip an entire directory--and most helpful to skip a directory and all subdirectories. That way I can skip, for example, /usr since none of my code lives there and I typically have no interest in debugging through 3rd party code. So I extended the 'skip' command in gdb to support a new type 'dir'. I can now do this in gdb:
skip dir /usr
and then I'm never stopped in any of my 3rd party headers.
Here's a webpage w/ this info + the patch if it helps anyone: info & patch to skip directories in GDB
It appears that this isn't possible in GDB. I've filed a bug.
Meanwhile, gdb has the skip function command. Just execute it when you are inside the uninteresting function and it will not bother you again.
skip file is also very useful to get rid of the STL internals.
As Justin has said, it has been added in gdb 7.4. For more details, take a look at the documentation.
Related
If I do C-u M-x recompile inside a buffer that's not the *compilation* buffer, (i.e. the source file for instance), I get this error - "Wrong type argument: consp, nil" after it prompts for the compilation command. Why is this? I want to run recompile interactively as comint works, sometimes outside the compilation buffer. How do I do this?
Try using emacs -Q, just to be sure (yes, I know you said you commented out all of your init file, but just to be sure -- and it's a lot easier to do than comment-out everything).
Next, set debug-on-error to t -- You can do M-x toggle-debug-on-error to do that, if you prefer.
Next, provoke the error and look at the debugger *Backtrace*. It will show you not only which function raised the error because it expected a cons and got nil instead, but also what function called it, passing the bad argument. And so on down the stack.
If necessary, you can click mouse-2 on functions on the stack (at the left, to see their source code. Or put the cursor on them and use C-h f to see their doc -- in particular, what arguments they expect and what their return values should be.
In this way it's pretty easy to find the code that is the culprit. (Most likely, in spite of what you said, it is some non-vanilla Emacs Lisp code you loaded somehow.)
Also, state your emacs version : M-x emacs-version. If you are using a development snapshot then the problem could come from vanilla code (i.e., emacs -Q); otherwise, that's not so likely.
Also, you say you get the error after it prompts you. Immediately after it prompts, before you type anything? After you type a command name and hit RET? Try to be more specific.
Update after your comment:
Load library compile.el (not .elc). Then do M-x debug-on-entry recompile, then step through the debugger using d when function recompile is entered. What you are interested in is when compilation-start is called (applied to its args).
It seems that the value of compilation-arguments that is passed to it is no good. The command name you enter at the prompt becomes the first of the list of compilation-arguments. The others are taken from when you last invoked compile: recompile just reuses the same arguments (except the command name): (mode name-function highlight-regexp)mode name-function highlight-regexp).
However, be aware that compilation-arguments is buffer-local. So if you changed to a different buffer then its value is likely not what you need. You need the value from your last compile, so you should do the recompile in the same buffer where you did compile.
(FWIW, I don't use (re)compile myself, as I don't develop software anymore. I just took a look at the source code.)
Such kind of errors usually depicts a problem with your configuration. Try to investigate messages buffer output. There can be some clues there.
And of course, it is normal to call a recompile command from a buffer with your code. It is a convention to bind it to C-c C-c.
I'm currently in a Python interactive interpreter session. I have a function that I know is doing something funky, so I want to step through it in a debugger session. I know the file name and line number of the function.
Is there any way for me to now set a breakpoint in the start of that function, then run it and step through it? Without having to open an editor, locate the file, locate the function, manually insert import pdb; pdb.set_trace(), saving the file, then go back to the interpreter, reload the module the function came from and running it? Not to mention that if I forgot to remove the pdb trace that'd spell trouble later.
Summarizing the question: If I'm in a normal Python interpreter session (or iPython), is it possible to set a breakpoint somewhere and start debugging, without having to actually edit in the code pdb.set_trace() somewhere?
I can't believe I missed this, but I just glanced over the pdb documentation a second time and realized that all the run* functions do pretty much exactly what I want. They don't let me set a specific line as a breakpoint, but I can pass the function and the arguments I want to use, and it will break on the first line of the function:
import pdb
pdb.runcall(my_wonky_function, "arg1", "arg2", *myargs)
Well actually it broke at a mystical location called "EOF":
(Pdb) list
[EOF]
and I had to step twice before I got to the first line of the function, but that's hardly a problem.
I'm using GCC 4.7.2. My code is rather heavy on template, STL and boost usage. When I compile and there is an error in some class or function that is derived from or uses some boost/STL functionality, I get error messages showing spectacularly hideous return types and/or function arguments for my classes/function.
My question:
Is there a prettyprint type of thing for GCC warnings/errors containing boost/STL types, so that the return types shown in error messages correspond to what I've typed in the code, or at least, become more intelligible?
I have briefly skimmed through this question, however, that is about GDB rather than GCC...
I've also come across this pretty printer in Haskell, but that just seems to add structure, not take away (mostly) unneeded detail...
Any other suggestions?
I asked a similar question, where someone suggested I try gccfilter. It's a Perl script that re-formats the output of g++ and colorizes it, shortens it, hides full pathnames, and lots more.
Actually, that suggestion answers this question really well too: it's capable of hiding unneeded detail and pretty-printing both STL and boost types. So: I'll leave this here as an answer too.
The only drawback I could see is that g++ needs to be called from within the script (i.e., piping to it is not possible at the time). I suspect that's easily fixed, and in any case, it's a relatively minor issue.
You could try STLfilt as mentioned in 'C++ Template Metaprogramming' by David Abrahms & Alesky Gurtovoy.
The book contains a chapter on template message diagnostics. It suggests using the STLFilt /showback:N to eliminate compiler backtrace material in order to get simplified output.
Can somebody please enlighten me as to what the command line flag to CMake might be that will make it print out all the compile/link commands it executes?
I can't find this anywhere in the documentation. Many hours of my life have just evaporated. I'd just like to verify it's doing what I think it is, (then banish the infernal build system altogether and replace it with a GNU Makefile).
Thank you!
The verbose argument should do what you want.
Content copied (with format adjusted slightly) here for future reference:
CMake/Verbose output
CMake has a nice colored output which hides the commandline. This is pretty to look at in the long run but sometimes when you write your configurations you want to know if you got all the compiler flags right. There is two ways to disable the pretty output, well, it's essentialy the same but still two different ways.
The first way is to simply run make with the additional argument "VERBOSE=1". This will show each command being run for this session, which is the most useful way to see if the flags is correct:
make VERBOSE=1
The second way is to permanently disable the pretty output in your CMakeLists.txt by setting CMAKE_VERBOSE_MAKEFILE:
set( CMAKE_VERBOSE_MAKEFILE on )
Content is available under Attribution-ShareAlike 2.5 unless otherwise noted.
Setting CMAKE_VERBOSE_MAKEFILE Works but the generator must be make. Documentation seems to assume this the case. Should probably be explicitly noted there.
This question HAS had to be asked before, so it kills me to ask it again, but I can't find it for all of my google and searching stackoverflow.
I'm porting a bunch of linux code to windows, and a good chunk of it makes the assumption that everything is automatically initialized to zero or null.
int whatever;
char* something;
...and then immediately doing something that may leave 'something' null, and testing against 'something'
if(something == NULL)
{
.......
}
I would REALLY like not to have to go back throughout this code and say:
int whatever = 0;
char* something = NULL;
Even though that is the proper way to deal with it. It's just very time consuming.
Otherwise, I declare a variable, and it's initialized to something crazy if I don't set it myself.
This option doesn't exist in MSVC, and honestly, whoever coded your application made a big mistake. That code is not portable, as C/C++ say that uninitialized variables have an undefined value. I suggest setting the "treat warnings as errors" option and recompiling; MSVC should give you a warning every time a variable is used without being initialized.
No - there's no option to do that in MSVC.
Debug builds will initialize them with something else (0xcc I think), but not zero. Unfortunately, your code is bugged and needs fixed (of course this applies only to automatic variables -for statics and globals it's fine to assume they're zero initialized). I'm surprised there was any compiler that supported that behavior - if there's an option to do that in GCC, I haven't heard of it (but I'm no expert in the dusty corners of GCC).
You may hear that an earlier version of MSVC would init variables to zero in debug builds (similar to the way 0xcc is used in VS 2005), but as far as I know that's untrue.
edit ----------
Well, I'll be damned - GCC does (or did?) have the -finit-local-zero option. Looks like it's there mostly for Fortran support, I think.
I'd suggest using compiler warnings about using uninitialized variables to help you catch 99% of your problems. I know it's not a great bit of work, but it should be done if at all possible.
Interestingly, MSVC now does have the ability to do this. The Microsoft Security team wrote a blog post about it here, and there's a CppCon talk here.
Unfortunately, it doesn't seem like this option is exposed to the public. This page lists a bunch of 'hidden MSVC flags', and it includes an option called -initall, so that might be it.
What I ended-up doing was switching to /w4. At this level, it caught most of the "yeah, that's going to be an issue" areas of initialization. Otherwise, there's nothing that can change everything from being 0xcccccccc on initialization to 0x00000000 that I saw.
Massive thanks to everyone for answering this, and yes, we will tighten it up in the future.