f68f85b52b
GDB currently crashes with infinite recursion, if you set a breakpoint
on a function inside a namespace that includes a template on its fully
qualified name, and, the template's name is also used as typedef in
the global scope that expands to a name that includes the template
name in its qualified name. For example, from the testcase added by
this commit:
namespace NS1 { namespace NS2 {
template<typename T> struct Templ1
{
T x;
Templ1 (object_p) {}
}} // namespace NS1::NS2
using Templ1 = NS1::NS2::Templ1<unsigned>;
Setting a breakpoint like so:
(gdb) break NS1::NS2::Templ1<int>::Templ1(NS1::NS2::object*)
Results in infinite recursion, with this cycle (started by
cp_canonicalize_string_full) repeating until the stack is exhausted:
...
#1709 0x000000000055533c in inspect_type (info=0x38ff720, ret_comp=0xd83be10, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:267
#1710 0x0000000000555a6f in replace_typedefs (info=0x38ff720, ret_comp=0xd83be10, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:475
#1711 0x0000000000555a36 in replace_typedefs (info=0x38ff720, ret_comp=0xd83be70, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:470
#1712 0x0000000000555800 in replace_typedefs_qualified_name (info=0x38ff720, ret_comp=0xd839470, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:389
#1713 0x0000000000555a8c in replace_typedefs (info=0x38ff720, ret_comp=0xd839470, finder=0x0, data=0x0) at /home/pedro/gdb/mygit/src/gdb/cp-support.c:479
...
The demangle component tree for that symbol name looks like this:
d_dump tree for NS1::NS2::Templ1<int>::Templ1(NS1::NS2::object*):
typed name
qualified name
name 'NS1'
qualified name
name 'NS2'
qualified name
template <<<<<<<<<<
name 'Templ1'
template argument list
builtin type int
name 'Templ1'
function type
argument list
pointer
qualified name
name 'NS1'
qualified name
name 'NS2'
name 'object'
The recursion starts at replace_typedefs_qualified_name, which doesn't
handle the "template" node, and thus doesn't realize that the template
name actually has the fully qualified name NS1::NS2::Templ1.
replace_typedefs_qualified_name calls into replace_typedefs on the
template node, and that ends up in inspect_type looking up for a
symbol named "Templ1", which finds the global namespace typedef, which
itself expands to NS1::NS2::Templ1. GDB then tries replacing typedefs
in that newly expanded name, which ends up again in
replace_typedefs_qualified_name, trying to expand a fully qualified
name with "NS::NS2::Templ1<unsigned>" in its name, which results in
recursion whenever the template node is reached.
Fix this by teaching replace_typedefs_qualified_name how to handle
template nodes. It needs handling in two places: the first spot
handles the symbol above; the second spot handles a symbol like this,
from the new test:
(gdb) b NS1::NS2::grab_it(NS1::NS2::Templ1<int>*)
d_dump tree for NS1::NS2::grab_it(NS1::NS2::Templ1<int>*):
typed name
qualified name
name 'NS1'
qualified name
name 'NS2'
name 'grab_it'
function type
argument list
pointer
qualified name
name 'NS1'
qualified name
name 'NS2'
template <<<<<<<<
name 'Templ1'
template argument list
builtin type int
What's different in this case is that the template node appears on the
right child node of a qualified name, instead of on the left child.
The testcase includes a test that checks whether template aliases are
correctly replaced by GDB too. That fails with GCC due to GCC PR
95437, which makes GDB not know about a typedef for
"NS1::NS2::AliasTempl<int>". GCC emits a typedef named
"NS1::NS2::AliasTempl" instead, with no template parameter info. The
test passes with Clang (5.0.2 at least). See more details here:
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95437
gdb/ChangeLog:
2020-05-30 Pedro Alves <palves@redhat.com>
* cp-support.c (replace_typedefs_template): New.
(replace_typedefs_qualified_name): Handle
DEMANGLE_COMPONENT_TEMPLATE.
gdb/testsuite/ChangeLog:
2020-05-30 Pedro Alves <palves@redhat.com>
* gdb.linespec/cp-replace-typedefs-ns-template.cc: New.
* gdb.linespec/cp-replace-typedefs-ns-template.exp: New.
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