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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 initialized 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 structures  are  in
       an  inconsistent	 state,	or that	its C procedures have been called in a
       manner inconsistent with	their documentation,  it  calls	 Tcl_Panic  to
       display a message describing the	error and abort	the process.  The for-
       mat  argument is	a format string	describing how to format the remaining
       arguments arg into an error message, according to the  same  formatting
       rules  used  by	the  printf  family of functions.  The same formatting
       rules are also used by the built-in Tcl command format.

       In a freshly loaded Tcl library,	Tcl_Panic prints the  formatted	 error
       message to the standard error file of the process, and then calls abort
       to  terminate the process.  Tcl_Panic does not return. On Windows, when
       a debugger is running, the formatted error message is sent to  the  de-
       bugger  instead.	If the windows executable does not have	a stderr chan-
       nel (e.g. wish.exe), then a system dialog box is	used  to  display  the
       panic message.

       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. 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 indi-
       cates 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 suitable for the application
       or the platform.

       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	exten-
       sion 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				      8.4			  Tcl_Panic(3)

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