82 lines
6.4 KiB
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82 lines
6.4 KiB
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<!-- Common Lisp HyperSpec (TM), version 7.0 generated by Kent M. Pitman on Mon, 11-Apr-2005 2:31am EDT -->
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<TITLE>CLHS: Variable *BREAK-ON-SIGNALS*</TITLE>
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<A NAME="STbreak-on-signalsST"><I>Variable</I> <B>*BREAK-ON-SIGNALS*</B></A> <P>
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<P><B>Value Type:</B><P>
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<P>
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a <A REL=DEFINITION HREF="26_glo_t.htm#type_specifier"><I>type specifier</I></A>. <P>
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<P><B>Initial Value:</B><P>
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<P>
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<A REL=DEFINITION HREF="a_nil.htm#nil"><B>nil</B></A>. <P>
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<P><B>Description:</B><P>
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<P>
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When <TT>(typep </TT><I>condition</I><TT> *break-on-signals*)</TT> returns <A REL=DEFINITION HREF="26_glo_t.htm#true"><I>true</I></A>, calls to <A REL=DEFINITION HREF="f_signal.htm#signal"><B>signal</B></A>, and to other <A REL=DEFINITION HREF="26_glo_o.htm#operator"><I>operators</I></A> such as <A REL=DEFINITION HREF="f_error.htm#error"><B>error</B></A> that implicitly call <A REL=DEFINITION HREF="f_signal.htm#signal"><B>signal</B></A>, enter the debugger prior to <I>signaling</I> the <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A>. <P>
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The <A REL=DEFINITION HREF="a_contin.htm#continue"><B>continue</B></A> <A REL=DEFINITION HREF="26_glo_r.htm#restart"><I>restart</I></A> can be used to continue with the normal <I>signaling</I> process when a break occurs process due to <A REL=DEFINITION HREF="#STbreak-on-signalsST"><B>*break-on-signals*</B></A>. <P>
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<P><B>Examples:</B><P>
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<P>
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<PRE>
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*break-on-signals* => NIL
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(ignore-errors (error 'simple-error :format-control "Fooey!"))
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=> NIL, #<SIMPLE-ERROR 32207172>
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(let ((*break-on-signals* 'error))
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(ignore-errors (error 'simple-error :format-control "Fooey!")))
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>> Break: Fooey!
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>> BREAK entered because of *BREAK-ON-SIGNALS*.
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>> To continue, type :CONTINUE followed by an option number:
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>> 1: Continue to signal.
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>> 2: Top level.
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>> Debug> :CONTINUE 1
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>> Continue to signal.
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=> NIL, #<SIMPLE-ERROR 32212257>
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(let ((*break-on-signals* 'error))
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(error 'simple-error :format-control "Fooey!"))
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>> Break: Fooey!
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>> BREAK entered because of *BREAK-ON-SIGNALS*.
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>> To continue, type :CONTINUE followed by an option number:
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>> 1: Continue to signal.
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>> 2: Top level.
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>> Debug> :CONTINUE 1
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>> Continue to signal.
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>> Error: Fooey!
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>> To continue, type :CONTINUE followed by an option number:
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>> 1: Top level.
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>> Debug> :CONTINUE 1
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>> Top level.
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</PRE>
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</TT> <P>
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<P><B>Affected By:</B> None.
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<P>
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<P><B>See Also:</B><P>
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<P>
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<A REL=DEFINITION HREF="f_break.htm#break"><B>break</B></A>, <A REL=DEFINITION HREF="f_signal.htm#signal"><B>signal</B></A>, <A REL=DEFINITION HREF="f_warn.htm#warn"><B>warn</B></A>, <A REL=DEFINITION HREF="f_error.htm#error"><B>error</B></A>, <A REL=DEFINITION HREF="f_typep.htm#typep"><B>typep</B></A>, <A REL=CHILD HREF="09_a.htm">Section 9.1 (Condition System Concepts)</A> <P>
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<P><B>Notes:</B><P>
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<P>
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<A REL=DEFINITION HREF="#STbreak-on-signalsST"><B>*break-on-signals*</B></A> is intended primarily for use in debugging code that does signaling. When setting <A REL=DEFINITION HREF="#STbreak-on-signalsST"><B>*break-on-signals*</B></A>, the user is encouraged to choose the most restrictive specification that suffices. Setting <A REL=DEFINITION HREF="#STbreak-on-signalsST"><B>*break-on-signals*</B></A> effectively violates the modular handling of <A REL=DEFINITION HREF="26_glo_c.htm#condition"><I>condition</I></A> signaling. In practice, the complete effect of setting <A REL=DEFINITION HREF="#STbreak-on-signalsST"><B>*break-on-signals*</B></A> might be unpredictable in some cases since the user might not be aware of the variety or number of calls to <A REL=DEFINITION HREF="f_signal.htm#signal"><B>signal</B></A> that are used in code called only incidentally. <P>
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<P>
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<A REL=DEFINITION HREF="#STbreak-on-signalsST"><B>*break-on-signals*</B></A> enables an early entry to the debugger but such an entry does not preclude an additional entry to the debugger in the case of operations such as <A REL=DEFINITION HREF="f_error.htm#error"><B>error</B></A> and <A REL=DEFINITION HREF="f_cerror.htm#cerror"><B>cerror</B></A>. <P>
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<P><HR>The following <A REL=META HREF="../Front/X3J13Iss.htm">X3J13 cleanup issues</A>, <I>not part of the specification</I>, apply to this section:<P><UL><LI> <A REL=CHILD HREF="../Issues/iss020.htm">BREAK-ON-WARNINGS-OBSOLETE:REMOVE</A><LI> <A REL=CHILD HREF="../Issues/iss170.htm">FORMAT-STRING-ARGUMENTS:SPECIFY</A><P></UL><HR>
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