From swmcd@world.std.com

sub AUTOLOAD {
[...]
  no strict 'refs';
  *$AUTOLOAD = sub () { $val };
  goto &$AUTOLOAD;
}

  *$AUTOLOAD = sub () { $val };
  ^^
The autoloaded sub is declared with a prototype, which causes an error
if &$AUTOLOAD doesn't have the same prototype when the assignment
executes.

So if I have a constant in a .h file

  #define FOO 17

and I try to get to it from Perl

  print FOO();

I get an error

  Prototype mismatch​: sub Foo​::FOO vs () at blib/lib/Foo.pm line 40.

unless I predeclare FOO() with the correct prototype

  sub FOO ();

Is this a bug or a feature?

- SWM

world​:~/PM/dev/Foo>perl -V
Summary of my perl5 (5.0 patchlevel 5 subversion 3) configuration​:
  Platform​:
  osname=irix, osvers=6.2, archname=IP19-irix
  uname='irix64 world 6.2 03131016 ip19 '
  hint=recommended, useposix=true, d_sigaction=define
  usethreads=undef useperlio=undef d_sfio=undef
  Compiler​:
  cc='cc -n32', optimize=' ', gccversion=
  cppflags='-D_BSD_TYPES -D_BSD_TIME -woff -I/usr/local/include
-DLANGUAGE_C'
  ccflags ='-D_BSD_TYPES -D_BSD_TIME -woff 1009,1110,1184
-I/usr/local/include -DLANGUAGE_C'
  stdchar='unsigned char', d_stdstdio=define, usevfork=false
  intsize=4, longsize=4, ptrsize=4, doublesize=8
  d_longlong=define, longlongsize=8, d_longdbl=define,
longdblsize=16
  alignbytes=8, usemymalloc=y, prototype=define
  Linker and Libraries​:
  ld='cc -n32', ldflags =' -L/usr/local/lib32 -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib32 /lib32 /lib /usr/lib
  libs=-lm -lc
  libc=/usr/lib32/libc.so, so=so, useshrplib=false,
libperl=libperl.a
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags=' '
  cccdlflags=' ', lddlflags='-n32 -shared -L/usr/local/lib32
-L/usr/local/lib'

Characteristics of this binary (from libperl)​:
  Built under irix
  Compiled at Sep 22 1999 10​:45​:43
  @​INC​:
  /home/abhaile/swmcd/perl/lib/5.00503/IP19-irix
  /home/abhaile/swmcd/perl/lib/5.00503
  /home/abhaile/swmcd/perl/lib/site_perl/5.005/IP19-irix
  /home/abhaile/swmcd/perl/lib/site_perl/5.005
  .

From @gsar

On Mon, 27 Dec 1999 01​:21​:53 EST, Steven W McDougall wrote​:

h2xs generates AUTOLOAD() like this

sub AUTOLOAD {
[...]
no strict 'refs';
*$AUTOLOAD = sub () { $val };
goto &$AUTOLOAD;
}

*$AUTOLOAD = sub () { $val };
^^
The autoloaded sub is declared with a prototype, which causes an error
if &$AUTOLOAD doesn't have the same prototype when the assignment
executes.

So if I have a constant in a .h file

#define FOO 17

and I try to get to it from Perl

print FOO();

I get an error

Prototype mismatch​: sub Foo​::FOO vs () at blib/lib/Foo.pm line 40.

unless I predeclare FOO() with the correct prototype

sub FOO ();

Is this a bug or a feature?

It is a feature. You are expected to define constant subs with an empty
prototype. IIRC, the version of h2ph in 5.00503 will do this for you.

Sarathy
gsar@​ActiveState.com

From The RT System itself

feature, not a bug.