[lldb-dev] How to get function name without arguments type/value/name?

[Jeffrey Tan via lldb-dev]

Hi Greg,

Thanks for the explanation. Even we strip the arguments we definitely will
provide a UI for users to toggle arguments type/name/values. It's just,
with argument types, the function name can be really long and hard to read:
[image: Inline image 1]

I was surprised that I need to strip out arguments manually because in
command line I can do "settings set frame-format [...%{
*function.name-without-args*}]" telling lldb to print callstack(using bt
command) without arguments. My understanding is that the get function name
without arguments exists because may not be exposed in python API yet. Is
this not true?

// bt command output after settings set frame-format [...%{
*function.name-without-args*}...]
 * frame #0: 0x0000000000403372 min`main + 586 at minimal.cpp:46
    frame #1: 0x00007f9a44c050f6 libc.so.6`__libc_start_main + 246
    frame #2: 0x0000000000402fb8 min`_start + 41 at start.S:122

Jeffrey

On Thu, Apr 21, 2016 at 2:49 PM, Greg Clayton <gclayton at apple.com> wrote:

> The difference is how the debug info is emitted in the DWARF. Functions
> that come from C++ will have mangled names. These mangled names contain the
> arguments. If a function has a mangled name we will demangle it and display
> that. You can easily strip this if you want to by looking for the first "("
> character and stripping the contents. We don't do anything like this. The
> main issue you will run into is if you have code like:
>
>
> int foo(int f)
> {
>     return f*2; // Break here...
> }
>
> float foo(float d)
> {
>     return (float)foo((int)d);
> }
>
> int main(int argc, const char **argv)
> {
>     float f = float(2.3);
>     return 0;
> }
>
>
> If you set a breakpoint at "Break here" and run you will currently get:
>
> foo(int) + 16
> foo(float) + 23
> main + 25
>
> But you are saying you would rather see:
>
> foo + 16
> foo + 23
> main + 25
>
> Or:
>
> foo(...) + 16
> foo(...) + 23
> main + 25
>
> "main" is funny because C++ compilers will often 'extern "C"' the function
> auto magically. This will stop it from getting a mangled name and stop us
> from showing "main(int, const char **)" as the function name.
>
> The other reason you might not want to strip anything from the actual name
> is what happens when you are debugging another language? If you strip any
> text between "(" and ")", you might ruin a stack frame for the "q" language
> that has a function name like "foo.bar.baz{int (hello)}" and display this
> as "foo.bar.baz{int ()}". So any stripping you do, you will want to only do
> this for specific languages. We do have "const char *
> SBFunction::GetDisplayName()", but we currently only do something different
> for Swift (the new Apple language). You can't change the output of that for
> C++.
>
> Personally I like to see all of the arguments that uniquely identify each
> function, but that is me. So anything you do in your debugger, you will
> want to make that configurable.
>
> Greg
>
>
> > On Apr 21, 2016, at 1:45 PM, Jeffrey Tan via lldb-dev <
> lldb-dev at lists.llvm.org> wrote:
> >
> > Hi,
> >
> > I call SBFrame.name to get function name and display in our debugger
> callstack window. However, this seems to include arguments types
> sometimes.(Btw: why it includes arguments types for subFunction but not
> main() in screenshot?)
> >
> > <Screen Shot 2016-04-21 at 1.40.55 PM.png>
> >
> > This is fine for small function, but can be really long if the function
> has a lot of arguments and the arguments are of template type.
> >
> > Is there any way to only get the function name without arguments types?
> >
> > I have tried ""settings set frame-format [..]" " which seems to only
> apply to "bt" command.
> > I have tried SBFrame.function.name the same result.
> >
> > Did I miss anything?
> > Jeffrey
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20160421/1368a8e6/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: Screen Shot 2016-04-19 at 23.13.43.png
Type: image/png
Size: 344755 bytes
Desc: not available
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20160421/1368a8e6/attachment-0001.png>