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  format-
       ting 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.

       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 suitable for the applica-
       tion 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									8.4							      Tcl_Panic(3)