GDB supports the Rust
Programming Language. Type- and value-printing, and expression
parsing, are reasonably complete. However, there are a few
peculiarities and holes to be aware of.
- Linespecs (see Specify Location) are never relative to the current
crate. Instead, they act as if there were a global namespace of
crates, somewhat similar to the way
extern crate behaves.
That is, if GDB is stopped at a breakpoint in a function in
crate ‘A’, module ‘B’, then
break B::f will attempt
to set a breakpoint in a function named ‘f’ in a crate named
As a consequence of this approach, linespecs also cannot refer to
items using ‘self::’ or ‘super::’.
- Because GDB implements Rust name-lookup semantics in
expressions, it will sometimes prepend the current crate to a name.
For example, if GDB is stopped at a breakpoint in the crate
print ::x::y will try to find the symbol
However, since it is useful to be able to refer to other crates when
debugging, GDB provides the
extern extension to
circumvent this. To use the extension, just put
a path expression to refer to the otherwise unavailable “global”
In the above example, if you wanted to refer to the symbol ‘y’ in
the crate ‘x’, you would use
print extern x::y.
- The Rust expression evaluator does not support “statement-like”
expressions such as
match, or lambda expressions.
- Tuple expressions are not implemented.
- The Rust expression evaluator does not currently implement the
Drop trait. Objects that may be created by the evaluator will
never be destroyed.
- GDB does not implement type inference for generics. In order
to call generic functions or otherwise refer to generic items, you
will have to specify the type parameters manually.
- GDB currently uses the C++ demangler for Rust. In most
cases this does not cause any problems. However, in an expression
context, completing a generic function name will give syntactically
invalid results. This happens because Rust requires the ‘::’
operator between the function name and its generic arguments. For
example, GDB might provide a completion like
crate::f<u32>, where the parser would require
- As of this writing, the Rust compiler (version 1.8) has a few holes in
the debugging information it generates. These holes prevent certain
features from being implemented by GDB:
- Method calls cannot be made via traits.
- Operator overloading is not implemented.
- When debugging in a monomorphized function, you cannot use the generic
- The type
Self is not available.
use statements are not available, so some names may not be
available in the crate.