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| 129 | .\" ======================================================================== |
| 130 | .\" |
| 131 | .IX Title "CLAN 1" |
| 132 | .TH CLAN 1 "2002-09-28" "perl v5.8.0" "User Contributed Perl Documentation" |
| 133 | .SH "NAME" |
| 134 | Carp::Clan \- Report errors from perspective of caller of a "clan" of modules |
| 135 | .SH "SYNOPSIS" |
| 136 | .IX Header "SYNOPSIS" |
| 137 | .Vb 1 |
| 138 | \& carp - warn of errors (from perspective of caller) |
| 139 | .Ve |
| 140 | .PP |
| 141 | .Vb 1 |
| 142 | \& cluck - warn of errors with stack backtrace |
| 143 | .Ve |
| 144 | .PP |
| 145 | .Vb 1 |
| 146 | \& croak - die of errors (from perspective of caller) |
| 147 | .Ve |
| 148 | .PP |
| 149 | .Vb 1 |
| 150 | \& confess - die of errors with stack backtrace |
| 151 | .Ve |
| 152 | .PP |
| 153 | .Vb 2 |
| 154 | \& use Carp::Clan qw(^MyClan::); |
| 155 | \& croak "We're outta here!"; |
| 156 | .Ve |
| 157 | .PP |
| 158 | .Vb 2 |
| 159 | \& use Carp::Clan; |
| 160 | \& confess "This is how we got here!"; |
| 161 | .Ve |
| 162 | .SH "DESCRIPTION" |
| 163 | .IX Header "DESCRIPTION" |
| 164 | This module is based on "\f(CW\*(C`Carp.pm\*(C'\fR\*(L" from Perl 5.005_03. It has been |
| 165 | modified to skip all package names matching the pattern given in |
| 166 | the \*(R"use\*(L" statement inside the \*(R"\f(CW\*(C`qw()\*(C'\fR" term (or argument list). |
| 167 | .PP |
| 168 | Suppose you have a family of modules or classes named \*(L"Pack::A\*(R", |
| 169 | \&\*(L"Pack::B\*(R" and so on, and each of them uses "\f(CW\*(C`Carp::Clan qw(^Pack::);\*(C'\fR" |
| 170 | (or at least the one in which the error or warning gets raised). |
| 171 | .PP |
| 172 | Thus when for example your script \*(L"tool.pl\*(R" calls module \*(L"Pack::A\*(R", |
| 173 | and module \*(L"Pack::A\*(R" calls module \*(L"Pack::B\*(R", an exception raised in |
| 174 | module \*(L"Pack::B\*(R" will appear to have originated in \*(L"tool.pl\*(R" where |
| 175 | \&\*(L"Pack::A\*(R" was called, and not in \*(L"Pack::A\*(R" where \*(L"Pack::B\*(R" was called, |
| 176 | as the unmodified "\f(CW\*(C`Carp.pm\*(C'\fR" would try to make you believe \f(CW\*(C`:\-)\*(C'\fR. |
| 177 | .PP |
| 178 | This works similarly if \*(L"Pack::B\*(R" calls \*(L"Pack::C\*(R" where the |
| 179 | exception is raised, etcetera. |
| 180 | .PP |
| 181 | In other words, this blames all errors in the "\f(CW\*(C`Pack::*\*(C'\fR" modules |
| 182 | on the user of these modules, i.e., on you. \f(CW\*(C`;\-)\*(C'\fR |
| 183 | .PP |
| 184 | The skipping of a clan (or family) of packages according to a pattern |
| 185 | describing its members is necessary in cases where these modules are |
| 186 | not classes derived from each other (and thus when examining \f(CW@ISA\fR |
| 187 | (as in the original "\f(CW\*(C`Carp.pm\*(C'\fR" module) doesn't help). |
| 188 | .PP |
| 189 | The purpose and advantage of this is that a \*(L"clan\*(R" of modules can work |
| 190 | together (and call each other) and throw exceptions at various depths |
| 191 | down the calling hierarchy and still appear as a monolithic block (as |
| 192 | though they were a single module) from the perspective of the caller. |
| 193 | .PP |
| 194 | In case you just want to ward off all error messages from the module |
| 195 | in which you "\f(CW\*(C`use Carp::Clan\*(C'\fR\*(L", i.e., if you want to make all error |
| 196 | messages or warnings to appear to originate from where your module |
| 197 | was called (this is what you usually used to \*(R"\f(CW\*(C`use Carp;\*(C'\fR" for \f(CW\*(C`;\-)\*(C'\fR), |
| 198 | instead of in your module itself (which is what you can do with a |
| 199 | \&\*(L"die\*(R" or \*(L"warn\*(R" anyway), you do not need to provide a pattern, |
| 200 | the module will automatically provide the correct one for you. |
| 201 | .PP |
| 202 | I.e., just "\f(CW\*(C`use Carp::Clan;\*(C'\fR\*(L" without any arguments and call \*(R"carp\*(L" |
| 203 | or \*(R"croak" as appropriate, and they will automatically defend your |
| 204 | module against all blames! |
| 205 | .PP |
| 206 | In other words, a pattern is only necessary if you want to make |
| 207 | several modules (more than one) work together and appear as though |
| 208 | they were only one. |
| 209 | .Sh "Forcing a Stack Trace" |
| 210 | .IX Subsection "Forcing a Stack Trace" |
| 211 | As a debugging aid, you can force "\f(CW\*(C`Carp::Clan\*(C'\fR\*(L" to treat a \*(R"croak\*(L" as |
| 212 | a \*(R"confess\*(L" and a \*(R"carp\*(L" as a \*(R"cluck". In other words, force a detailed |
| 213 | stack trace to be given. This can be very helpful when trying to |
| 214 | understand why, or from where, a warning or error is being generated. |
| 215 | .PP |
| 216 | This feature is enabled either by \*(L"importing\*(R" the non-existent symbol |
| 217 | \&'verbose', or by setting the global variable "\f(CW$Carp::Clan::Verbose\fR" |
| 218 | to a true value. |
| 219 | .PP |
| 220 | You would typically enable it by saying |
| 221 | .PP |
| 222 | .Vb 1 |
| 223 | \& use Carp::Clan qw(verbose); |
| 224 | .Ve |
| 225 | .PP |
| 226 | Note that you can both specify a \*(L"family pattern\*(R" and the string \*(L"verbose\*(R" |
| 227 | inside the "\f(CW\*(C`qw()\*(C'\fR\*(L" term (or argument list) of the \*(R"use\*(L" statement, but |
| 228 | consider that a pattern of packages to skip is pointless when \*(R"verbose" |
| 229 | causes a full stack trace anyway. |
| 230 | .SH "BUGS" |
| 231 | .IX Header "BUGS" |
| 232 | The "\f(CW\*(C`Carp::Clan\*(C'\fR\*(L" routines don't handle exception objects currently. |
| 233 | If called with a first argument that is a reference, they simply |
| 234 | call \*(R"\f(CW\*(C`die()\*(C'\fR\*(L" or \*(R"\f(CW\*(C`warn()\*(C'\fR", as appropriate. |