NOTES.org

Notes

Multi-Index Containers

The printer included here can only print ordered (unique or non-unique) and sequenced indexes. Hashed and random-access indexes are not currently supported, though with the default settings, the printer will capture them and display an appropriate message.

It is possible to specify which index to use for printing a specific container dynamically, from inside GDB. See examples/test-multi-index.gdb.

Trivial Printers

This package provides a convenient way to define trivial printers from inside gdb. The trivial printers are great when the value you want to print can be easily described (in python) as a function of the value that would otherwise be printed. Two specific examples of this are:

1. Some_Struct contains a field height; we want to print that field instead of the whole struct.
2. Some_Class has Some_Base_Class as 2nd base class; we want to cast objects into that base class before printing.

Here is the syntax:

##### e.g. 1
py boost.add_trivial_printer("Some_Struct", lambda v: v['height'])
##### e.g. 2
py boost.add_trivial_printer("Some_Object", lambda v: v.cast(v.type.fields()[1].type))
##### check trivial printers are registered
info pretty-print global trivial
##### disable trivial printers
disable pretty-print global trivial;Some_Type

NOTE: the command prefixed by py uses python syntax, not gdb syntax, e.g., v['height'] instead of v.height. For a glossary of the syntax, see Getting Started in HACKING.org.

For other examples, see examples/test-intrusive-advanced.cpp and examples/test-intrusive-advanced.gdb.

At Function

The package provides a gdb convenience function $at() for printing a specific element inside a container. This should work with any container, including the ones in the Standard Library (provided you have installed the libstdc++ package that contains pretty printers for them). For example:

cat <<"EOF" >a.cpp
#include <list>
std::list< int > l = { 1, 5, 17, 42 };
void done() {}
int main() { done(); }
EOF
cat <<"EOF" >a.gdb
break done
run
print l
print $at(l, 2)
quit
EOF
g++ -O0 -g3 -ggdb -std=c++11 -Wall -Wextra -pedantic -o a a.cpp
gdb a -x a.gdb |& grep '^\$'
$1 = std::list = {[0] = 1, [1] = 5, [2] = 17, [3] = 42}
$2 = "17"