[lldb-dev] Navigating STL types

[Greg Clayton via lldb-dev]

You could add an explicit instantiation of your template for C++ types you need. 

Example without:

#include <cstdio>
#include <vector>

int main (int argc, char const *argv[])
{
  std::vector<int> ints = { 1,2,3,4 };
  for (auto i: ints)
    printf("%i\n", i);
  return 0;
}


(lldb) target create "a.out"
(lldb) b /auto i/
(lldb) r
(lldb) p ints.size()
error: Couldn't lookup symbols:
  __ZNKSt3__16vectorIiNS_9allocatorIiEEE4sizeEv


But add the explicit instantiation:

#include <cstdio>
#include <vector>

template class std::vector<int>; /// <<<<<<<<<

int main (int argc, char const *argv[])
{
  std::vector<int> ints = { 1,2,3,4 };
  for (auto i: ints)
    printf("%i\n", i);
  return 0;
}


(lldb) target create "a.out"
(lldb) b /auto i/
(lldb) r
(lldb) p ints.size()
(std::__1::vector<int, std::__1::allocator<int> >::size_type) $0 = 4


So you could have some piece of code somewhere in your project:

#ifndef NDEBUG
/// Explicitly instantiate any STL stuff you need in order to debug
#endif

GDB is probably working around this by doing things for you without running the code that doesn’t exist.

Greg


> On Jan 23, 2017, at 3:58 PM, Andreas Yankopolus via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> 
> How can I navigate STL types using their overloaded operators and member functions (e.g., “[]” and “.first()” for vectors) ? For example, take a C++ source file with:
> 
> std::vector<std::string> v;
> v.push_back("foo”);
> 
> Breaking after this statement in lldb and typing "p v[0]" would be reasonably expected to return "foo", but it gives a symbol lookup error. Similarly, “p v.first()” gives an error that there’s no member named “first”. I’m seeing this issue with clang/llvm 3.9 and 4.0 nightlies on Ubuntu 16.10 and with Apple’s versions on MacOS Sierra.
> 
> Internet rumor (e.g., this discussion <http://stackoverflow.com/questions/39680320/printing-debugging-libc-stl-with-xcode-lldb/39731933>) says this is aggressive inlining of STL code. I’m compiling in clang++ with “-O0 -g -glldb”.
> 
> In comparison, gdb prints the value of v[0] just fine when compiled with gdb.
> 
> What am I doing wrong?
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