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Diffstat (limited to 'pod/perlsub.pod')
| -rw-r--r-- | pod/perlsub.pod | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/pod/perlsub.pod b/pod/perlsub.pod index bd3eb18154..c83f2da336 100644 --- a/pod/perlsub.pod +++ b/pod/perlsub.pod @@ -754,6 +754,34 @@ starts scribbling on your @_ parameter list. This is all very powerful, of course, and should be used only in moderation to make the world a better place. +=head2 Constant Functions + +Functions with a prototype of C<()> are potential candidates for +inlining. If the result after optimization and constant folding is a +constant then it will be used in place of new-style calls to the +function. Old-style calls (that is, calls made using C<&>) are not +affected. + +All of the following functions would be inlined. + + sub PI () { 3.14159 } + sub ST_DEV () { 0 } + sub ST_INO () { 1 } + + sub FLAG_FOO () { 1 << 8 } + sub FLAG_BAR () { 1 << 9 } + sub FLAG_MASK () { FLAG_FOO | FLAG_BAR } + + sub OPT_BAZ () { 1 } + sub BAZ_VAL () { + if (OPT_BAZ) { + return 23; + } + else { + return 42; + } + } + If you redefine a subroutine which was eligible for inlining you'll get a mandatory warning. (You can use this warning to tell whether or not a particular subroutine is considered constant.) The warning is |