lldb可以显示typedef的实际类型吗？

Question

I'm debugging some template code, and would like lldb to show me the actual type (c-type) of a frame variable instead of a monstrously complex typedef. The actual type would be something like "int" or "unsigned char", but it shows me only the typedef as if it had no knowledge of the specific template instance.

For example:

template <typename T>
struct helper
{
    using type = long;
};

int main(int argc, const char * argv[]) {

    using var_t = typename helper<short>::type;

    var_t foo = 1;
}

Stopping at a breakpoint set on "var_t foo = 1" shows

foo = (var_t)0

I really need to see something like

foo = (long)0

Is there any way to do this, or to find out what the resolved type is?

I'm using XCode 7.3 and lldb-350.0.21.3

Answer 1

There is no way to tell the variable printer to show the resolved type rather than the declared type of a variable. You can find out what the resolved type for a typedef is using the type search mode of image lookup :

(lldb) image lookup -t var_t
1 match found in /private/tmp/foo:
id = {0x000000b2}, name = "var_t", byte-size = 8, decl = foo.cpp:9, compiler_type = "typedef var_t"
     typedef 'var_t': id = {0x00000043}, name = "helper<short>::type", byte-size = 8, decl = foo.cpp:4, compiler_type = "typedef helper<short>::type"
     typedef 'helper<short>::type': id = {0x000000eb}, name = "long int", qualified = "long", byte-size = 8, compiler_type = "long"

Here's another way to get the same info from the Python API if you want to use that:

(lldb) script
Python Interactive Interpreter. To exit, type 'quit()', 'exit()' or Ctrl-D.
>>> foo_var = lldb.frame.FindVariable("foo")
>>> foo_type = foo_var.GetType()
>>> print foo_type
typedef var_t
>>> print foo_type.GetCanonicalType()
long

If this is something you need to do a lot, you could write a Python based lldb command to print the fully resolved type. There's info here:

http://lldb.llvm.org/python-reference.html

on how to do that.