ABI (Debugging with GDB)
22.7 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 current ABI.
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 platform provides.
When GDB is debugging the AArch64 architecture, it provides a “Newlib” OS ABI. This is useful for handling
longjmp when debugging binaries that use the NEWLIB C library. The “Newlib” OS ABI can be selected by
set osabi Newlib.
- Show the OS ABI currently in use.
- With no argument, show the list of registered available OS ABI’s.
set osabi abi
- Set the current OS ABI to
Generally, the way that an argument of type
float is passed to a function depends on whether the function is prototyped. For a prototyped (i.e. ANSI/ISO style) function,
float arguments are passed unchanged, according to the architecture’s convention for
float. For unprototyped (i.e. 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 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 functions.
Show the current setting of promoting
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 “auto”.
- Show the C++ ABI currently in use.
- 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.