[Bug 42920] New: LLDB fails to evaluate expression with template class type

Bug ID 42920
Summary LLDB fails to evaluate expression with template class type
Product lldb
Version unspecified
Hardware PC
OS All
Status NEW
Severity enhancement
Priority P
Component All Bugs
Assignee lldb-dev@lists.llvm.org
Reporter sfunkenhauser@google.com
CC jdevlieghere@apple.com, llvm-bugs@lists.llvm.org

LLDB fails to evaluate expressions with template class types.

Simple example:
template <typename T> class foo
  uint32_t data;

foo<int> test;

int main() {
  return 0;

I set a breakpoint on main and try to evaluate the following expression:
(lldb) p sizeof(foo<int>)
error: implicit instantiation of undefined template 'foo<int>'
template is declared here

The debug information is available (It's not being optimized out), and printing
'test' works just fine:
$ readelf --debug-dump a.out | grep foo
    <41>   DW_AT_name        : (indirect string, offset: 0xa): foo<int>
    <49>   DW_AT_name        : (indirect string, offset: 0x0): foo
    3f          foo<int>

Quoting Jim Ingham from a discussion on lldb-dev@
"LLDB uses clang as its expression parser, which when it sees foo<int>
apparently wants to find a decl called "foo" first, which we don't really have
in the abstract."