Looking up templated type in gdb's Python

Asked Nov 25 '22 at 13:42

Active Nov 25 '22 at 14:16

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I've loaded up two versions of a C++ library in gdb, opened up the built-in Python interpreter, and run

import gdb
gdb.lookup_type('Foo<Bar>')

In one version, it works just fine. However, in the other, I get

gdb.error: No type named Foo<Bar>.

I've confirmed that both the Foo template as well as the Bar class still exist in the latter library's source. What could explain the failure to look up the type? Does Foo<Bar> have to "exist" in the source in that combination for the type to show up under gdb?

Running file on the libraries produces

libfoo.so: ELF 64-bit LSB shared object, ARM aarch64, version 1 (SYSV), dynamically linked, BuildId[xxHash]=..., with debug_info, not stripped

edited Nov 25 '22 at 14:16

asked Nov 25 '22 at 13:42

Daniel Walker

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Yes, the program needs to have an instantiation of `Foo` somewhere. `gdb` is not a C++ compiler, it will not instantiate templates for you. – n. m. could be an AI Nov 25 '22 at 14:29
So, would I use `nm` to see what types are exported? – Daniel Walker Nov 25 '22 at 14:33
I don't think `nm` can show this. Try `objdump --dwarf=info` instead. – n. m. could be an AI Nov 25 '22 at 15:29
Do you know what in the `objdump` output would indicate that `gdb.lookup_type` will succeed? I see several things like `Foo` which show up but still fail under `lookup_type`. – Daniel Walker Nov 25 '22 at 16:20

Looking up templated type in gdb's Python

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