exception(3C)

NAME
     exc_resume, exc_setjmp, find_fde, find_fde_name, exc_unwind,
     exc_unwind_name - Exception handling facility

SYNOPSIS
     #include <exception.h>

     #if (defined(_LANGUAGE_C) || defined(_LANGUAGE_C_PLUS_PLUS))

     #if (_MIPS_SIM == _MIPS_SIM_NABI32)

     Dwarf_Fde find_fde(long pc);

     Dwarf_Fde find_fde(Elf32_Addr *pc);

     Dwarf_Fde find_fde_name(Elf32_Addr *pc, char **name);

     #else /* if (_MIPS_SIM == _MIPS_SIM_ABI64) */

     Dwarf_Fde find_fde(Elf64_Addr *pc);

     Dwarf_Fde find_fde_name(Elf64_Addr *pc, char **name);

     #endif

     void exc_unwind(struct sigcontext *scp, Dwarf_Fde fde);

     void exc_unwind_name(struct sigcontext *scp, Dwarf_Fde fde, char
     **name);

     int exc_resume(struct sigcontext *scp);

     void exc_setjmp(struct sigcontext *scp);

IMPLEMENTATION
     IRIX systems

DESCRIPTION
          NOTE:  This version (4.0) of exception handling facility is
          totally different from the (3.xx) versions.  This version
          extracts information from the .debug_frame section instead of the
          runtime procedure table as in the prior releases.  The old
          functions (exception_dispatcher, find_rpd,
          set_unhandled_exception and unwind) are no longer supported.

     To handle exceptions from UNIX signals and to minimize the cost at
     runtime until an exception is encountered, the loader collects per-
     procedure exception information and frame information so that the
     stack unwinds easily at the point of exception.

     The data structure Dwarf_Fde is specified in the (.debug_frame)
     section.  See the dwarf(4) man page for additional information.

     At runtime the following procedures will be provided in libexc.so:

     find_fde will return the Frame Description Entry(FDE) specified by the
     pc argument, if there is one, otherwise it will return NULL.

     find_fde_name does the same thing as find_fde but in addition returns
     the name of the procedure through the parameter name.  Use free to
     deallocate the returned strings after they are used.  (See the
     free(3C) man page for details on its use.)

     exc_unwind will take the sigcontext scp argument and virtually unwind
     by changing the fields to reflect the next frame on the stack.  A
     sigreturn call can be called with this scp upon return and will return
     to the frame unwind set up.  The fde argument is used as the Frame
     Description Entry argument.  If it is NULL, exc_unwind will call
     find_fde on scp->sc_pc to get it.  If exc_unwind is unable to unwind
     the stack, it will set the sc_pc field of the scp parameter to 1,
     indicating invalid address.

     exc_unwind_name does the same thing as exc_unwind but in addition
     returns the name of the procedure of the current sigcontext through
     the parameter name.  Use free to deallocate the returned strings after
     they are used.  (See the free(3C) man page for details on its use.)

     exc_setjmp is like setjmp, except that it saves V0 and also sets a
     special magic number so that exc_resume can tell which degree of
     restoration is required.

     exc_resume is like longjmp, except that it restores the v0 that
     exc_setjmp saved and performs one of the three different degress of
     restoration, according to the magic number in the sigcontext.

EXAMPLES
          cc  main.o -lexc -ldwarf -lelf

SEE ALSO
     free(3C), libexc(3), malloc(3C)

     dwarf(4)

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