21.6. Configuring the current ABI
gdb can determine the ABI (Application Binary Interface) of your
application automatically. However, sometimes you need to override its
conclusions. Use these commands to manage gdb's view of the
One gdb configuration can debug binaries for multiple operating
system targets, either via remote debugging or native emulation.
gdb will autodetect the OS ABI (Operating System ABI) in use,
but you can override its conclusion using the set osabi command.
One example where this is useful is in debugging of binaries which use
an alternate C library (e.g. uClibc for gnu/Linux) which does
not have the same identifying marks that the standard C library for your
- show osabi
Show the OS ABI currently in use.
- set osabi
With no argument, show the list of registered available OS ABI's.
- set osabi abi
Set the current OS ABI to abi.
Generally, the way that an argument of type float is passed to a
function depends on whether the function is prototyped. For a prototyped
(that is, ANSI/ISO style) function, float arguments are passed unchanged,
according to the architecture's convention for float. For unprototyped
(that is, K&R style) functions, float arguments are first promoted to type
double and then passed.
Unfortunately, some forms of debug information do not reliably indicate whether
a function is prototyped. If gdb calls a function that is not marked
as prototyped, it consults set coerce-float-to-double.
- set coerce-float-to-double, set coerce-float-to-double on
Arguments of type float will be promoted to double when passed
to an unprototyped function. This is the default setting.
- set coerce-float-to-double off
Arguments of type float will be passed directly to unprototyped
gdb needs to know the ABI used for your program's C++
objects. The correct C++ ABI depends on which C++ compiler was
used to build your application. gdb only fully supports
programs with a single C++ ABI; if your program contains code using
multiple C++ ABI's or if gdb can not identify your
program's ABI correctly, you can tell gdb which ABI to use.
Currently supported ABI's include "gnu-v2", for g++ versions
before 3.0, "gnu-v3", for g++ versions 3.0 and later, and
"hpaCC" for the HP ANSI C++ compiler. Other C++ compilers may
use the "gnu-v2" or "gnu-v3" ABI's as well. The default setting is
- show cp-abi
Show the C++ ABI currently in use.
- set cp-abi
With no argument, show the list of supported C++ ABI's.
- set cp-abi abi, set cp-abi auto
Set the current C++ ABI to abi, or return to automatic detection.