Tcl_Panic(3)

Tcl_Panic(3)         Tcl Library Procedures          Tcl_Panic(3)

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NAME

     Tcl_Panic,  Tcl_PanicVA,  Tcl_SetPanicProc  -  report  fatal
     error and abort

SYNOPSIS

     #include <tcl.h>

     void
     Tcl_Panic(format, arg, arg, ...)

     void
     Tcl_PanicVA(format, argList)

     void
     Tcl_SetPanicProc(panicProc)

ARGUMENTS

     const char* format (in)                A printf-style format
                                            string.

      arg (in)                              Arguments    matching
                                            the format string.

     va_list argList (in)                   An argument  list  of
                                            arguments    matching
                                            the  format   string.
                                            Must  have  been ini-
                                            tialized        using
                                            va_start, and cleared
                                            using va_end.

     Tcl_PanicProc *panicProc (in)          Procedure  to  report
                                            fatal  error  message
                                            and abort.

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DESCRIPTION

     When the Tcl library detects that its internal  data  struc-
     tures are in an inconsistent state, or that its C procedures
     have been called in a manner inconsistent with  their  docu-
     mentation,  it calls Tcl_Panic to display a message describ-
     ing the error and abort the process.  The format argument is
     a format string describing how to format the remaining argu-
     ments arg into an error message, according to the same  for-
     matting  rules  used by the printf family of functions.  The
     same formatting rules are also used by the built-in Tcl com-
     mand format.

Tcl                     Last change: 8.4                        1

Tcl_Panic(3)         Tcl Library Procedures          Tcl_Panic(3)

     In a freshly loaded Tcl library, Tcl_Panic prints  the  for-
     matted  error message to the standard error file of the pro-
     cess,  and  then  calls  abort  to  terminate  the  process.
     Tcl_Panic does not return.

     Tcl_SetPanicProc may be  used  to  modify  the  behavior  of
     Tcl_Panic.   The  panicProc  argument  should match the type
     Tcl_PanicProc:

          typedef void Tcl_PanicProc(
                  const char *format,
                  arg, arg,...);

     After  Tcl_SetPanicProc  returns,  any   future   calls   to
     Tcl_Panic  will call panicProc, passing along the format and
     arg arguments.  To maintain consistency with the callers  of
     Tcl_Panic,  panicProc  must  not return; it must call abort.
     panicProc should avoid making calls into the Tcl library, or
     into  other  libraries  that may call the Tcl library, since
     the original call to Tcl_Panic indicates the Tcl library  is
     not in a state of reliable operation.

     The typical use of Tcl_SetPanicProc arranges for  the  error
     message  to  be displayed or reported in a manner more suit-
     able for the application or the platform.   As  an  example,
     the Windows implementation of wish calls Tcl_SetPanicProc to
     force all panic messages to be displayed in a system  dialog
     box,  rather  than  to be printed to the standard error file
     (usually not visible under Windows).

     Although the primary callers of Tcl_Panic are the procedures
     of  the  Tcl library, Tcl_Panic is a public function and may
     be called by any extension or  application  that  wishes  to
     abort  the  process  and  have a panic message displayed the
     same way that panic messages from Tcl will be displayed.

     Tcl_PanicVA is the same as Tcl_Panic except that instead  of
     taking  a  variable number of arguments it takes an argument
     list.

SEE ALSO

     abort(3), printf(3), exec(n), format(n)

KEYWORDS

     abort, fatal, error

Tcl                     Last change: 8.4                        2