X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=vms%2Fperlvms.pod;h=53efdade2d2bdd60aaeb95446d7d7537522eb4c8;hb=fe2ae5081bc2e29bed890e921179e594deb788ec;hp=685e39cd9f8c6c9d7d6394c019832eff966ef5ec;hpb=fb38d079f941c715cfb0486ced0d003ca5964c75;p=p5sagit%2Fp5-mst-13.2.git diff --git a/vms/perlvms.pod b/vms/perlvms.pod index 685e39c..53efdad 100644 --- a/vms/perlvms.pod +++ b/vms/perlvms.pod @@ -367,6 +367,30 @@ The PERL5LIB and PERLLIB logical names work as documented in L, except that the element separator is '|' instead of ':'. The directory specifications may use either VMS or Unix syntax. +=head1 PERL_VMS_EXCEPTION_DEBUG + +The PERL_VMS_EXCEPTION_DEBUG being defined as "ENABLE" will cause the VMS +debugger to be invoked if a fatal exception that is not otherwise +handled is raised. The purpose of this is to allow debugging of +internal Perl problems that would cause such a condition. + +This allows the programmer to look at the execution stack and variables to +find out the cause of the exception. As the debugger is being invoked as +the Perl interpreter is about to do a fatal exit, continuing the execution +in debug mode is usally not practical. + +Starting Perl in the VMS debugger may change the program execution +profile in a way that such problems are not reproduced. + +The C function can be used to test this functionality from within +a program. + +In typical VMS style, only the first letter of the value of this logical +name is actually checked in a case insensitive mode, and it is considered +enabled if it is the value "T","1" or "E". + +This logical name must be defined before Perl is started. + =head1 Command line =head2 I/O redirection and backgrounding @@ -543,6 +567,7 @@ DECC$POSIX_COMPLIANT_PATHNAMES to defined as 3, and operating in a DECC$FILENAME_UNIX_REPORT mode. lchown, link, lstat, readlink, symlink + =over 4 =item File tests @@ -626,6 +651,45 @@ C to insure that you'll get the proper value: return 1; } + +=item die + +C will force the native VMS exit status to be an SS$_ABORT code +if neither of the $! or $? status values are ones that would cause +the native status to be interpreted as being what VMS classifies as +SEVERE_ERROR severity for DCL error handling. + +When the future POSIX_EXIT mode is active, C, the native VMS exit +status value will have either one of the C<$!> or C<$?> or C<$^E> or +the UNIX value 255 encoded into it in a way that the effective original +value can be decoded by other programs written in C, including Perl +and the GNV package. As per the normal non-VMS behavior of C if +either C<$!> or C<$?> are non-zero, one of those values will be +encoded into a native VMS status value. If both of the UNIX status +values are 0, and the C<$^E> value is set one of ERROR or SEVERE_ERROR +severity, then the C<$^E> value will be used as the exit code as is. +If none of the above apply, the UNIX value of 255 will be encoded into +a native VMS exit status value. + +Please note a significant difference in the behavior of C in +the future POSIX_EXIT mode is that it does not force a VMS +SEVERE_ERROR status on exit. The UNIX exit values of 2 through +255 will be encoded in VMS status values with severity levels of +SUCCESS. The UNIX exit value of 1 will be encoded in a VMS status +value with a severity level of ERROR. This is to be compatible with +how the VMS C library encodes these values. + +The minimum severity level set by C in a future POSIX_EXIT mode +may be changed to be ERROR or higher before that mode becomes fully active +depending on the results of testing and further review. If this is +done, the behavior of c in the future POSIX_EXIT will close enough +to the default mode that most DCL shell scripts will probably not notice +a difference. + +See C<$?> for a description of the encoding of the UNIX value to +produce a native VMS status containing it. + + =item dump Rather than causing Perl to abort and dump core, the C @@ -817,9 +881,10 @@ and not traditional VMS behavior. =item utime LIST -Since ODS-2, the VMS file structure for disk files, does not keep -track of access times, this operator changes only the modification -time of the file (VMS revision date). +This operator changes only the modification time of the file (VMS +revision date) on ODS-2 volumes and ODS-5 volumes without access +dates enabled. On ODS-5 volumes with access dates enabled, the +true access time is modified. =item waitpid PID,FLAGS @@ -1029,39 +1094,51 @@ compiled with the _POSIX_EXIT macro set, the status value will contain the actual value of 0 to 255 returned by that program on a normal exit. -With the _POSIX_EXIT macro set, the exit code of zero is represented -as 1, and the values from 2 to 255 are encoded by the equation -VMS_status = 0x35a000 + (exit_code * 8) + 1. And in the special -case of value 1, VMS_status = 0x35a000 + 8 + 2 + 0x10000000. +With the _POSIX_EXIT macro set, the UNIX exit value of zero is +represented as a VMS native status of 1, and the UNIX values +from 2 to 255 are encoded by the equation: + + VMS_status = 0x35a000 + (unix_value * 8) + 1. + +And in the special case of unix value 1 the encoding is: + + VMS_status = 0x35a000 + 8 + 2 + 0x10000000. For other termination statuses, the severity portion of the -subprocess' exit status: if the severity was success or +subprocess' exit status is used: if the severity was success or informational, these bits are all 0; if the severity was warning, they contain a value of 1; if the severity was error or fatal error, they contain the actual severity bits, -which turns out to be a value of 2 for error and 4 for fatal error. +which turns out to be a value of 2 for error and 4 for severe_error. +Fatal is another term for the severe_error status. As a result, C<$?> will always be zero if the subprocess' exit status indicated successful completion, and non-zero if a warning or error occurred or a program compliant with encoding _POSIX_EXIT values was run and set a status. -How can you tell the difference? You can not unless you look at -the ${^CHILD_ERROR_NATIVE} code. The ${^CHILD_ERROR_NATIVE} code -returns the actual VMS status value and check the severity bits. -If the severity bits are clear, then the numeric value is code -passed back from the application. +How can you tell the difference between a non-zero status that is +the result of a VMS native error status or an encoded UNIX status? +You can not unless you look at the ${^CHILD_ERROR_NATIVE} value. +The ${^CHILD_ERROR_NATIVE} value returns the actual VMS status value +and check the severity bits. If the severity bits are equal to 1, +then if the numeric value for C<$?> is between 2 and 255 or 0, then +C<$?> accurately reflects a value passed back from a UNIX application. +If C<$?> is 1, and the severity bits indicate a VMS error (2), then +C<$?> is from a UNIX application exit value. In practice, Perl scripts that call programs that return _POSIX_EXIT -type status codes will be expecting those codes, and programs that -call traditional VMS programs will be expecting the previous behavior. +type status values will be expecting those values, and programs that +call traditional VMS programs will either be expecting the previous +behavior or just checking for a non-zero status. -And success is always the code 0. +And success is always the value 0 in all behaviors. When the actual VMS termination status of the child is an error, -internally the C<$!> value will be set to the closest UNIX code to -that error so that Perl scripts that test for error messages will -see the expected UNIX style error message instead of a VMS message. +internally the C<$!> value will be set to the closest UNIX errno +value to that error so that Perl scripts that test for error +messages will see the expected UNIX style error message instead +of a VMS message. Conversely, when setting C<$?> in an END block, an attempt is made to convert the POSIX value into a native status intelligible to @@ -1070,12 +1147,30 @@ is that setting C<$?> to zero results in the generic success value SS$_NORMAL, and setting C<$?> to a non-zero value results in the generic failure status SS$_ABORT. See also L. +With the future POSIX_EXIT mode set, setting C<$?> will cause the +new value to also be encoded into C<$^E> so that the either the +original parent or child exit status values of 0 to 255 +can be automatically recovered by C programs expecting _POSIX_EXIT +behavior. If both a parent and a child exit value are non-zero, then it +will be assumed that this is actually a VMS native status value to +be passed through. The special value of 0xFFFF is almost a NOOP as +it will cause the current native VMS status in the C library to +become the current native Perl VMS status, and is handled this way +as consequence of it known to not be a valid native VMS status value. +It is recommend that only values in range of normal UNIX parent or +child status numbers, 0 to 255 are used. + The pragma C makes C<$?> reflect the actual VMS exit status instead of the default emulation of POSIX status described above. This pragma also disables the conversion of non-zero values to SS$_ABORT when setting C<$?> in an END block (but zero will still be converted to SS$_NORMAL). +Do not use the pragma C with the future +POSIX_EXIT mode, as they are at times requesting conflicting +actions and the consequence of ignoring this advice will be +undefined to allow future improvements in the POSIX exit handling. + =item $| Setting C<$|> for an I/O stream causes data to be flushed