I want to examine the contents of a std::vector in gdb but I don't have access to _M_impl because I'm using icc, not gcc, how do I do it? Let's say it's a std::vector for the sake of simplicity.
There is a very nice answer here but this doesn't work if I use icc, the error message is "There is no member or method named _M_impl". There appears to be a nice debug toolset here but it also relies on _M_impl.
Not sure this will work with your vector, but it worked for me.
#include <string>
#include <vector>
int main() {
std::vector<std::string> vec;
vec.push_back("Hello");
vec.push_back("world");
vec.push_back("!");
return 0;
}
gdb:
(gdb) break source.cpp:8
(gdb) run
(gdb) p vec.begin()
$1 = {
_M_current = 0x300340
}
(gdb) p $1._M_current->c_str()
$2 = 0x3002fc "Hello"
(gdb) p $1._M_current +1
$3 = (string *) 0x300344
(gdb) p $3->c_str()
$4 = 0x30032c "world"
Generally when I deal with the container classes in a debugger, I build a reference to the element, as a local variable, so it is easy to see in the debugger, without mucking about in the container implementation.
Here is a contrived example.
vector<WeirdStructure> myWeird;
/* push back a lot of stuff into the vector */
size_t z;
for (z = 0; z < myWeird.size(); z++)
{
WeirdStructure& weird = myWeird[z];
/* at this point weird is directly observable by the debugger */
/* your code to manipulate weird goes here */
}
That is the idiom I use.
The std::vector template guarantees the data is stored contiguously. If you take the address of the front element (say, &v[0], for instance), you can access any other element in the vector through a C-style array. That doesn't require you to have the source code of the STL available to your debugger.
After messing with this some, it appears that v.front() and v.begin() are likely inlined and GDB isn't finding them. I'll keep looking, but personally I would simply add the line int* i = &v[0] to the source file, and then use GDB commands on i while debugging. Note that the compiler is free to remove that dead code. You may need to output the value of i to avoid that, or simply not crank up optimizations.
