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| <a name="Assembler-Commands-for-Exception-Regions"></a> |
| <h4 class="subsection">17.21.9 Assembler Commands for Exception Regions</h4> |
| |
| |
| <p>This describes commands marking the start and the end of an exception |
| region. |
| </p> |
| <dl> |
| <dt><a name="index-EH_005fFRAME_005fSECTION_005fNAME"></a>Macro: <strong>EH_FRAME_SECTION_NAME</strong></dt> |
| <dd><p>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. |
| <samp>crtstuff.c</samp> uses this macro to switch to the appropriate section. |
| </p> |
| <p>You should define this symbol if your target supports DWARF 2 frame |
| unwind information and the default definition does not work. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-EH_005fFRAME_005fIN_005fDATA_005fSECTION"></a>Macro: <strong>EH_FRAME_IN_DATA_SECTION</strong></dt> |
| <dd><p>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. |
| </p> |
| <p>Do not define this macro unless <code>TARGET_ASM_NAMED_SECTION</code> is |
| also defined. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-EH_005fTABLES_005fCAN_005fBE_005fREAD_005fONLY"></a>Macro: <strong>EH_TABLES_CAN_BE_READ_ONLY</strong></dt> |
| <dd><p>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. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-MASK_005fRETURN_005fADDR"></a>Macro: <strong>MASK_RETURN_ADDR</strong></dt> |
| <dd><p>An rtx used to mask the return address found via <code>RETURN_ADDR_RTX</code>, so |
| that it does not contain any extraneous set bits in it. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-DWARF2_005fUNWIND_005fINFO"></a>Macro: <strong>DWARF2_UNWIND_INFO</strong></dt> |
| <dd><p>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 |
| <code>INCOMING_RETURN_ADDR_RTX</code> and <code>OBJECT_FORMAT_ELF</code>), |
| GCC will provide a default definition of 1. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fEXCEPT_005fUNWIND_005fINFO"></a>Common Target Hook: <em>enum unwind_info_type</em> <strong>TARGET_EXCEPT_UNWIND_INFO</strong> <em>(struct gcc_options *<var>opts</var>)</em></dt> |
| <dd><p>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 <code>UI_TARGET</code>. If the target is to use the |
| <code>setjmp</code>/<code>longjmp</code>-based exception handling scheme, the hook |
| should return <code>UI_SJLJ</code>. If the target supports DWARF 2 frame unwind |
| information, the hook should return <code>UI_DWARF2</code>. |
| </p> |
| <p>A target may, if exceptions are disabled, choose to return <code>UI_NONE</code>. |
| This may end up simplifying other parts of target-specific code. The |
| default implementation of this hook never returns <code>UI_NONE</code>. |
| </p> |
| <p>Note that the value returned by this hook should be constant. It should |
| not depend on anything except the command-line switches described by |
| <var>opts</var>. In particular, the |
| setting <code>UI_SJLJ</code> 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. |
| </p> |
| <p>The default implementation of the hook first honors the |
| <samp>--enable-sjlj-exceptions</samp> configure option, then |
| <code>DWARF2_UNWIND_INFO</code>, and finally defaults to <code>UI_SJLJ</code>. If |
| <code>DWARF2_UNWIND_INFO</code> depends on command-line options, the target |
| must define this hook so that <var>opts</var> is used correctly. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fUNWIND_005fTABLES_005fDEFAULT"></a>Common Target Hook: <em>bool</em> <strong>TARGET_UNWIND_TABLES_DEFAULT</strong></dt> |
| <dd><p>This variable should be set to <code>true</code> if the target ABI requires unwinding |
| tables even when exceptions are not used. It must not be modified by |
| command-line option processing. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-DONT_005fUSE_005fBUILTIN_005fSETJMP"></a>Macro: <strong>DONT_USE_BUILTIN_SETJMP</strong></dt> |
| <dd><p>Define this macro to 1 if the <code>setjmp</code>/<code>longjmp</code>-based scheme |
| should use the <code>setjmp</code>/<code>longjmp</code> functions from the C library |
| instead of the <code>__builtin_setjmp</code>/<code>__builtin_longjmp</code> machinery. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-JMP_005fBUF_005fSIZE"></a>Macro: <strong>JMP_BUF_SIZE</strong></dt> |
| <dd><p>This macro has no effect unless <code>DONT_USE_BUILTIN_SETJMP</code> is also |
| defined. Define this macro if the default size of <code>jmp_buf</code> buffer |
| for the <code>setjmp</code>/<code>longjmp</code>-based exception handling mechanism |
| is not large enough, or if it is much too large. |
| The default size is <code>FIRST_PSEUDO_REGISTER * sizeof(void *)</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-DWARF_005fCIE_005fDATA_005fALIGNMENT"></a>Macro: <strong>DWARF_CIE_DATA_ALIGNMENT</strong></dt> |
| <dd><p>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 |
| <code>UNITS_PER_WORD</code>. The definition should be the negative minimum |
| alignment if <code>STACK_GROWS_DOWNWARD</code> is defined, and the positive |
| minimum alignment otherwise. See <a href="SDB-and-DWARF.html#SDB-and-DWARF">SDB and DWARF</a>. Only applicable if |
| the target supports DWARF 2 frame unwind information. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fTERMINATE_005fDW2_005fEH_005fFRAME_005fINFO"></a>Target Hook: <em>bool</em> <strong>TARGET_TERMINATE_DW2_EH_FRAME_INFO</strong></dt> |
| <dd><p>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 <code>EH_FRAME_SECTION_NAME</code> is defined, and |
| true otherwise. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fDWARF_005fREGISTER_005fSPAN"></a>Target Hook: <em>rtx</em> <strong>TARGET_DWARF_REGISTER_SPAN</strong> <em>(rtx <var>reg</var>)</em></dt> |
| <dd><p>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 <code>NULL_RTX</code>. |
| If not defined, the default is to return <code>NULL_RTX</code>. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fINIT_005fDWARF_005fREG_005fSIZES_005fEXTRA"></a>Target Hook: <em>void</em> <strong>TARGET_INIT_DWARF_REG_SIZES_EXTRA</strong> <em>(tree <var>address</var>)</em></dt> |
| <dd><p>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 <code>expand_builtin_init_dwarf_reg_sizes</code> after |
| filling in a single size corresponding to each hard register; |
| <var>address</var> is the address of the table. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fASM_005fTTYPE"></a>Target Hook: <em>bool</em> <strong>TARGET_ASM_TTYPE</strong> <em>(rtx <var>sym</var>)</em></dt> |
| <dd><p>This hook is used to output a reference from a frame unwinding table to |
| the type_info object identified by <var>sym</var>. It should return <code>true</code> |
| if the reference was output. Returning <code>false</code> will cause the |
| reference to be output using the normal Dwarf2 routines. |
| </p></dd></dl> |
| |
| <dl> |
| <dt><a name="index-TARGET_005fARM_005fEABI_005fUNWINDER"></a>Target Hook: <em>bool</em> <strong>TARGET_ARM_EABI_UNWINDER</strong></dt> |
| <dd><p>This flag should be set to <code>true</code> on targets that use an ARM EABI |
| based unwinding library, and <code>false</code> on other targets. This effects |
| the format of unwinding tables, and how the unwinder in entered after |
| running a cleanup. The default is <code>false</code>. |
| </p></dd></dl> |
| |
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