This describes commands marking the start and the end of an exception region.
If defined, a C string constant for the name of the section containing exception handling frame unwind information. If not defined, GCC will provide a default definition if the target supports named sections. crtstuff.c uses this macro to switch to the appropriate section.
You should define this symbol if your target supports DWARF 2 frame unwind information and the default definition does not work.
If defined, DWARF 2 frame unwind information will identified by specially named labels. The collect2 process will locate these labels and generate code to register the frames.
This might be necessary, for instance, if the system linker will not place the eh_frames in-between the sentinals from crtstuff.c, or if the system linker does garbage collection and sections cannot be marked as not to be collected.
Define this macro to 1 if your target is such that no frame unwind information encoding used with non-PIC code will ever require a runtime relocation, but the linker may not support merging read-only and read-write sections into a single read-write section.
An rtx used to mask the return address found via
that it does not contain any extraneous set bits in it.
Define this macro to 0 if your target supports DWARF 2 frame unwind
information, but it does not yet work with exception handling.
Otherwise, if your target supports this information (if it defines
GCC will provide a default definition of 1.
This hook defines the mechanism that will be used for exception handling
by the target. If the target has ABI specified unwind tables, the hook
UI_TARGET. If the target is to use the
longjmp-based exception handling scheme, the hook
UI_SJLJ. If the target supports DWARF 2 frame unwind
information, the hook should return
A target may, if exceptions are disabled, choose to return
This may end up simplifying other parts of target-specific code. The
default implementation of this hook never returns
Note that the value returned by this hook should be constant. It should
not depend on anything except the command-line switches described by
opts. In particular, the
UI_SJLJ must be fixed at compiler start-up as C pre-processor
macros and builtin functions related to exception handling are set up
depending on this setting.
The default implementation of the hook first honors the
--enable-sjlj-exceptions configure option, then
DWARF2_UNWIND_INFO, and finally defaults to
DWARF2_UNWIND_INFO depends on command-line options, the target
must define this hook so that opts is used correctly.
This variable should be set to
true if the target ABI requires unwinding
tables even when exceptions are not used. It must not be modified by
command-line option processing.
Define this macro to 1 if the
should use the
longjmp functions from the C library
instead of the
This macro has no effect unless
DONT_USE_BUILTIN_SETJMP is also
defined. Define this macro if the default size of
longjmp-based exception handling mechanism
is not large enough, or if it is much too large.
The default size is
FIRST_PSEUDO_REGISTER * sizeof(void *).
This macro need only be defined if the target might save registers in the
function prologue at an offset to the stack pointer that is not aligned to
UNITS_PER_WORD. The definition should be the negative minimum
STACK_GROWS_DOWNWARD is true, and the positive
minimum alignment otherwise. See DWARF. Only applicable if
the target supports DWARF 2 frame unwind information.
Contains the value true if the target should add a zero word onto the
end of a Dwarf-2 frame info section when used for exception handling.
Default value is false if
EH_FRAME_SECTION_NAME is defined, and
Given a register, this hook should return a parallel of registers to
represent where to find the register pieces. Define this hook if the
register and its mode are represented in Dwarf in non-contiguous
locations, or if the register should be represented in more than one
register in Dwarf. Otherwise, this hook should return
If not defined, the default is to return
Given a register, this hook should return the mode which the corresponding Dwarf frame register should have. This is normally used to return a smaller mode than the raw mode to prevent call clobbered parts of a register altering the frame register size
If some registers are represented in Dwarf-2 unwind information in
multiple pieces, define this hook to fill in information about the
sizes of those pieces in the table used by the unwinder at runtime.
It will be called by
filling in a single size corresponding to each hard register;
address is the address of the table.
This hook is used to output a reference from a frame unwinding table to
the type_info object identified by sym. It should return
if the reference was output. Returning
false will cause the
reference to be output using the normal Dwarf2 routines.
This flag should be set to
true on targets that use an ARM EABI
based unwinding library, and
false on other targets. This effects
the format of unwinding tables, and how the unwinder in entered after
running a cleanup. The default is