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+# Copyright 2003 Dave Abrahams
+# Copyright 2004 Vladimir Prus
+# Distributed under the Boost Software License, Version 1.0.
+# (See accompanying file LICENSE_1_0.txt or http://www.boost.org/LICENSE_1_0.txt)
+
+# Print a stack backtrace leading to this rule's caller. Each argument
+# represents a line of output to be printed after the first line of the
+# backtrace.
+#
+rule backtrace ( skip-frames prefix messages * : * )
+{
+ local frame-skips = 5 9 13 17 21 25 29 33 37 41 45 49 53 57 61 65 69 73 77 81 ;
+ local drop-elements = $(frame-skips[$(skip-frames)]) ;
+ if ! ( $(skip-frames) in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 )
+ {
+ ECHO "warning: backtrace doesn't support skipping $(skip-frames) frames;"
+ "using 1 instead." ;
+ drop-elements = 5 ;
+ }
+
+ local args = $(.args) ;
+ if $(.user-modules-only)
+ {
+ local bt = [ nearest-user-location ] ;
+ ECHO "$(prefix) at $(bt) " ;
+ for local n in $(args)
+ {
+ if $($(n))-is-not-empty
+ {
+ ECHO $(prefix) $($(n)) ;
+ }
+ }
+ }
+ else
+ {
+ # Get the whole backtrace, then drop the initial quadruples
+ # corresponding to the frames that must be skipped.
+ local bt = [ BACKTRACE ] ;
+ bt = $(bt[$(drop-elements)-]) ;
+
+ while $(bt)
+ {
+ local m = [ MATCH ^(.+)\\.$ : $(bt[3]) ] ;
+ ECHO $(bt[1]):$(bt[2]): "in" $(bt[4]) "from module" $(m) ;
+
+ # The first time through, print each argument on a separate line.
+ for local n in $(args)
+ {
+ if $($(n))-is-not-empty
+ {
+ ECHO $(prefix) $($(n)) ;
+ }
+ }
+ args = ; # Kill args so that this never happens again.
+
+ # Move on to the next quadruple.
+ bt = $(bt[5-]) ;
+ }
+ }
+}
+
+.args ?= messages 2 3 4 5 6 7 8 9 ;
+.disabled ?= ;
+.last-error-$(.args) ?= ;
+
+
+# try-catch --
+#
+# This is not really an exception-handling mechanism, but it does allow us to
+# perform some error-checking on our error-checking. Errors are suppressed after
+# a try, and the first one is recorded. Use catch to check that the error
+# message matched expectations.
+
+# Begin looking for error messages.
+#
+rule try ( )
+{
+ .disabled += true ;
+ .last-error-$(.args) = ;
+}
+
+
+# Stop looking for error messages; generate an error if an argument of messages
+# is not found in the corresponding argument in the error call.
+#
+rule catch ( messages * : * )
+{
+ .disabled = $(.disabled[2-]) ; # Pop the stack.
+
+ import sequence ;
+
+ if ! $(.last-error-$(.args))-is-not-empty
+ {
+ error-skip-frames 3 expected an error, but none occurred ;
+ }
+ else
+ {
+ for local n in $(.args)
+ {
+ if ! $($(n)) in $(.last-error-$(n))
+ {
+ local v = [ sequence.join $($(n)) : " " ] ;
+ v ?= "" ;
+ local joined = [ sequence.join $(.last-error-$(n)) : " " ] ;
+
+ .last-error-$(.args) = ;
+ error-skip-frames 3 expected \"$(v)\" in argument $(n) of error
+ : got \"$(joined)\" instead ;
+ }
+ }
+ }
+}
+
+
+rule error-skip-frames ( skip-frames messages * : * )
+{
+ if ! $(.disabled)
+ {
+ backtrace $(skip-frames) error: $(messages) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) ;
+ EXIT ;
+ }
+ else if ! $(.last-error-$(.args))
+ {
+ for local n in $(.args)
+ {
+ # Add an extra empty string so that we always have
+ # something in the event of an error
+ .last-error-$(n) = $($(n)) "" ;
+ }
+ }
+}
+
+if --no-error-backtrace in [ modules.peek : ARGV ]
+{
+ .no-error-backtrace = true ;
+}
+
+
+# Print an error message with a stack backtrace and exit.
+#
+rule error ( messages * : * )
+{
+ if $(.no-error-backtrace)
+ {
+ # Print each argument on a separate line.
+ for local n in $(.args)
+ {
+ if $($(n))-is-not-empty
+ {
+ if ! $(first-printed)
+ {
+ ECHO error: $($(n)) ;
+ first-printed = true ;
+ }
+ else
+ {
+ ECHO $($(n)) ;
+ }
+ }
+ }
+ EXIT ;
+ }
+ else
+ {
+ error-skip-frames 3 $(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) ;
+ }
+}
+
+
+# Same as 'error', but the generated backtrace will include only user files.
+#
+rule user-error ( messages * : * )
+{
+ .user-modules-only = 1 ;
+ error-skip-frames 3 $(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) ;
+}
+
+
+# Print a warning message with a stack backtrace and exit.
+#
+rule warning
+{
+ backtrace 2 warning: $(1) : $(2) : $(3) : $(4) : $(5) : $(6) : $(7) : $(8) : $(9) ;
+}
+
+
+# Convert an arbitrary argument list into a list with ":" separators and quoted
+# elements representing the same information. This is mostly useful for
+# formatting descriptions of arguments with which a rule was called when
+# reporting an error.
+#
+rule lol->list ( * )
+{
+ local result ;
+ local remaining = 1 2 3 4 5 6 7 8 9 ;
+ while $($(remaining))
+ {
+ local n = $(remaining[1]) ;
+ remaining = $(remaining[2-]) ;
+
+ if $(n) != 1
+ {
+ result += ":" ;
+ }
+ result += \"$($(n))\" ;
+ }
+ return $(result) ;
+}
+
+
+# Return the file:line for the nearest entry in backtrace which correspond to a
+# user module.
+#
+rule nearest-user-location ( )
+{
+ local bt = [ BACKTRACE ] ;
+
+ local result ;
+ while $(bt) && ! $(result)
+ {
+ local m = [ MATCH ^(.+)\\.$ : $(bt[3]) ] ;
+ local user-modules = ([Jj]amroot(.jam|.v2|)|([Jj]amfile(.jam|.v2|)|user-config.jam|site-config.jam|project-root.jam) ;
+
+ if [ MATCH $(user-modules) : $(bt[1]:D=) ]
+ {
+ result = $(bt[1]):$(bt[2]) ;
+ }
+ bt = $(bt[5-]) ;
+ }
+ return $(result) ;
+}
+
+
+# If optimized rule is available in Jam, use it.
+if NEAREST_USER_LOCATION in [ RULENAMES ]
+{
+ rule nearest-user-location ( )
+ {
+ local r = [ NEAREST_USER_LOCATION ] ;
+ return $(r[1]):$(r[2]) ;
+ }
+}
+
+
+rule __test__ ( )
+{
+ # Show that we can correctly catch an expected error.
+ try ;
+ {
+ error an error occurred : somewhere ;
+ }
+ catch an error occurred : somewhere ;
+
+ # Show that unexpected errors generate real errors.
+ try ;
+ {
+ try ;
+ {
+ error an error occurred : somewhere ;
+ }
+ catch an error occurred : nowhere ;
+ }
+ catch expected \"nowhere\" in argument 2 ;
+
+ # Show that not catching an error where one was expected is an error.
+ try ;
+ {
+ try ;
+ {
+ }
+ catch ;
+ }
+ catch expected an error, but none occurred ;
+}