ParseXS - handle #else and #endif without blank line prefixes

This patch makes it possible to omit some of the whitespace around
preprocessor directives. It teaches fetch_para() to understand
that a #else or #endif directive that does not end a #if that
was seen in the current "paragraph" should not be parsed as part
of that paragraph. This means that a conditional block that defines
the same sub under different define conditions need not have extra
whitespace after each sub definition.

MANIFEST

@@ -3710,6 +3710,7 @@ dist/ExtUtils-ParseXS/t/XSInclude.xsh				Test file for ExtUtils::ParseXS tests
 dist/ExtUtils-ParseXS/t/XSMore.xs				Test file for ExtUtils::ParseXS tests
 dist/ExtUtils-ParseXS/t/XSTest.pm				Test file for ExtUtils::ParseXS tests
 dist/ExtUtils-ParseXS/t/XSTest.xs				Test file for ExtUtils::ParseXS tests
+dist/ExtUtils-ParseXS/t/XSTightDirectives.xs			Test file for ExtUtils::ParseXS tests
 dist/ExtUtils-ParseXS/t/XSUsage.pm				ExtUtils::ParseXS tests
 dist/ExtUtils-ParseXS/t/XSUsage.xs				ExtUtils::ParseXS tests
 dist/ExtUtils-ParseXS/t/XSWarn.xs				ExtUtils::ParseXS tests

dist/ExtUtils-ParseXS/lib/ExtUtils/ParseXS.pm

@@ -1800,11 +1800,17 @@ sub fetch_para {
     $self->_process_module_xs_line($1, $2, $3);
   }
 
+  # count how many #ifdef levels we see in this paragraph
+  # decrementing when we see an endif. if we see an elsif
+  # or endif without a corresponding #ifdef then we dont
+  # consider it part of this paragraph.
+  my $if_level = 0;
   for (;;) {
     $self->_maybe_skip_pod;
 
     $self->_maybe_parse_typemap_block;
 
+    my $final;
     if ($self->{lastline} !~ /^\s*#/ # not a CPP directive
         # CPP directives:
         #    ANSI:    if ifdef ifndef elif else endif define undef
@@ -1825,6 +1831,31 @@ sub fetch_para {
     )
     {
       last if $self->{lastline} =~ /^\S/ && @{ $self->{line} } && $self->{line}->[-1] eq "";
+      if ($self->{lastline}=~/^#[ \t]*(if|ifn?def|elif|else|endif)\b/) {
+        my $type = $1; # highest defined capture buffer, "if" for any if like condition
+        if ($type =~ /^if/) {
+          if (@{$self->{line}}) {
+            # increment level
+            $if_level++;
+          } else {
+            $final = 1;
+          }
+        } elsif ($type eq "endif") {
+          if ($if_level) { # are we in an if that was started in this paragraph?
+            $if_level--;   # yep- so decrement to end this if block
+          } else {
+            $final = 1;
+          }
+        } elsif (!$if_level) {
+          # not in an #ifdef from this paragraph, thus
+          # this directive should not be part of this paragraph.
+          $final = 1;
+        }
+      }
+      if ($final and @{$self->{line}}) {
+        return 1;
+      }
+
       push(@{ $self->{line} }, $self->{lastline});
       push(@{ $self->{line_no} }, $self->{lastline_no});
     }
@@ -1838,12 +1869,18 @@ sub fetch_para {
 
     chomp $self->{lastline};
     $self->{lastline} =~ s/^\s+$//;
+    if ($final) {
+      last;
+    }
   }
 
   # Nuke trailing "line" entries until there's one that's not empty
   pop(@{ $self->{line} }), pop(@{ $self->{line_no} })
     while @{ $self->{line} } && $self->{line}->[-1] eq "";
 
+  #use Data::Dumper;
+  #warn Dumper("late",$self->{line},$self->{line_no}, $self->{lastline});
+
   return 1;
 }
 

dist/ExtUtils-ParseXS/t/001-basic.t

@@ -1,7 +1,7 @@
 #!/usr/bin/perl
 
 use strict;
-use Test::More tests => 20;
+use Test::More tests => 22;
 use Config;
 use DynaLoader;
 use ExtUtils::CBuilder;
@@ -222,6 +222,24 @@ like $stderr, '/No INPUT definition/', "Exercise typemap error";
 
 #####################################################################
 
+{ # tight cpp directives
+  my $pxs = ExtUtils::ParseXS->new;
+  tie *FH, 'Foo';
+  my $stderr = PrimitiveCapture::capture_stderr(sub {
+    $pxs->process_file(
+      filename => 'XSTightDirectives.xs',
+      output => \*FH,
+      prototypes => 1);
+  });
+  my $content = tied(*FH)->{buf};
+  my $count = 0;
+  $count++ while $content=~/^XS_EUPXS\(XS_My_do\)\n\{/mg;
+  is $stderr, undef, "No error expected from TightDirectives.xs";
+  is $count, 2, "Saw XS_MY_do definition the expected number of times";
+}
+
+#####################################################################
+
 sub Foo::TIEHANDLE { bless {}, 'Foo' }
 sub Foo::PRINT { shift->{buf} .= join '', @_ }
 sub Foo::content { shift->{buf} }

dist/ExtUtils-ParseXS/t/XSTightDirectives.xs

@@ -0,0 +1,21 @@
+MODULE = My PACKAGE = My
+
+#ifdef MYDEF123
+void
+do(dbh)
+   SV *dbh
+CODE:
+{
+   int x;
+   ++x;
+}
+#else
+void
+do(dbh)
+   SV *dbh
+CODE:
+{
+   int x;
+   ++x;
+}
+#endif