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 be placed in the data section even though the target supports named sections. This might be necessary, for instance, if the system linker does garbage collection and sections cannot be marked as not to be collected.
Do not define this macro unless
TARGET_ASM_NAMED_SECTIONis also defined.
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
RETURN_ADDR_RTX, so 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
OBJECT_FORMAT_ELF), 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 should return
UI_TARGET. If the target is to use the
longjmp-based exception handling scheme, the hook should return
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
UI_NONE. 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 setting
UI_SJLJmust 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_INFOdepends on command-line options, the target must define this hook so that opts is used correctly.
This variable should be set to
trueif 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
longjmp-based scheme should use the
longjmpfunctions from the C library instead of the
This macro has no effect unless
DONT_USE_BUILTIN_SETJMPis also defined. Define this macro if the default size of
jmp_bufbuffer for the
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 alignment if
STACK_GROWS_DOWNWARDis true, and the positive minimum alignment otherwise. See SDB and 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_NAMEis defined, and true otherwise.
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
NULL_RTX. 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
expand_builtin_init_dwarf_reg_sizesafter 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
trueif the reference was output. Returning
falsewill cause the reference to be output using the normal Dwarf2 routines.