Make it possible to specify source files that will only be used for shared libs

There are rare cases when an object file will only be used when
building a shared library.  To enable this, we introduce
SHARED_SOURCE:

    SHARED_SOURCE[libfoo]=dllmain.c
Reviewed-by: NAndy Polyakov <appro@openssl.org>

Configurations/README

@@ -358,6 +358,11 @@ sense at all to just have a rename like that (why not just use
 "libbar" everywhere?), it does make sense when it can be used
 conditionally.  See a little further below for an example.
 
+In some cases, it's desirable to include some source files in the
+shared form of a library only:
+
+    SHARED_SOURCE[libfoo]=dllmain.c
+
 For any file to be built, it's also possible to tell what extra
 include paths the build of their source files should use:
 

Configurations/README.design

@@ -233,6 +233,10 @@ indexes:
                SOURCE variables, and AS source files for programs and
                libraries.
 
+  shared_sources =>
+               a hash table just like 'sources', but only as source
+               files (object files) for building shared libraries.
+
 As an example, here is how the build.info files example from the
 section above would be digested into a %unified_info table:
 

Configurations/common.tmpl

@@ -92,9 +92,11 @@
          $OUT .= libobj2shlib(shlib => $unified_info{sharednames}->{$lib},
                               lib => $lib,
                               objs => [ map { (my $x = $_) =~ s|\.o$||; $x }
-                                        @{$unified_info{sources}->{$lib}} ],
+                                        (@{$unified_info{sources}->{$lib}},
+                                         @{$unified_info{shared_sources}->{$lib}}) ],
                               deps => [ reducedepends(resolvedepends($lib)) ],
                               %ordinals);
+         map { doobj($_, $lib, intent => "lib") } @{$unified_info{shared_sources}->{$lib}};
      }
      $OUT .= obj2lib(lib => $lib,
                      objs => [ map { (my $x = $_) =~ s|\.o$||; $x }
@@ -111,9 +113,11 @@
      return "" if $cache{$lib};
      $OUT .= obj2dso(lib => $lib,
                      objs => [ map { (my $x = $_) =~ s|\.o$||; $x }
-                               @{$unified_info{sources}->{$lib}} ],
+                               (@{$unified_info{sources}->{$lib}},
+                                @{$unified_info{shared_sources}->{$lib}}) ],
                      deps => [ resolvedepends($lib) ]);
-     map { doobj($_, $lib, intent => "dso") } @{$unified_info{sources}->{$lib}};
+     map { doobj($_, $lib, intent => "dso") } (@{$unified_info{sources}->{$lib}},
+                                               @{$unified_info{shared_sources}->{$lib}});
      $cache{$lib} = 1;
  }
 

Configure

@@ -1303,6 +1303,7 @@ if ($builder eq "unified") {
 
         my %ordinals = ();
         my %sources = ();
+        my %shared_sources = ();
         my %includes = ();
         my %depends = ();
         my %renames = ();
@@ -1382,6 +1383,9 @@ if ($builder eq "unified") {
             qr/^\s*SOURCE\[((?:\\.|[^\\\]])+)\]\s*=\s*(.*)\s*$/
             => sub { push @{$sources{$1}}, split(/\s+/, $2)
                          if !@skip || $skip[$#skip] > 0 },
+            qr/^\s*SHARED_SOURCE\[((?:\\.|[^\\\]])+)\]\s*=\s*(.*)\s*$/
+            => sub { push @{$shared_sources{$1}}, split(/\s+/, $2)
+                         if !@skip || $skip[$#skip] > 0 },
             qr/^\s*INCLUDE\[((?:\\.|[^\\\]])+)\]\s*=\s*(.*)\s*$/
             => sub { push @{$includes{$1}}, split(/\s+/, $2)
                          if !@skip || $skip[$#skip] > 0 },
@@ -1567,6 +1571,32 @@ EOF
             }
         }
 
+        foreach (keys %shared_sources) {
+            my $dest = $_;
+            my $ddest = cleanfile($buildd, $_, $blddir);
+            if ($unified_info{rename}->{$ddest}) {
+                $ddest = $unified_info{rename}->{$ddest};
+            }
+            foreach (@{$shared_sources{$dest}}) {
+                my $s = cleanfile($sourced, $_, $blddir);
+
+                # If it isn't in the source tree, we assume it's generated
+                # in the build tree
+                if (! -f $s) {
+                    $s = cleanfile($buildd, $_, $blddir);
+                }
+                # We recognise C and asm files
+                if ($s =~ /\.[csS]\b$/) {
+                    (my $o = $_) =~ s/\.[csS]\b$/.o/;
+                    $o = cleanfile($buildd, $o, $blddir);
+                    $unified_info{shared_sources}->{$ddest}->{$o} = 1;
+                    $unified_info{sources}->{$o}->{$s} = 1;
+                } else {
+                    die "unrecognised source file type for shared library: $s\n";
+                }
+            }
+        }
+
         foreach (keys %generate) {
             my $dest = $_;
             my $ddest = cleanfile($buildd, $_, $blddir);
@@ -1636,7 +1666,7 @@ EOF
         $unified_info{$_} = [ sort keys %{$unified_info{$_}} ];
     }
     # Two level structures
-    foreach my $l1 (("sources", "ldadd", "depends")) {
+    foreach my $l1 (("sources", "shared_sources", "ldadd", "depends")) {
         foreach my $l2 (sort keys %{$unified_info{$l1}}) {
             $unified_info{$l1}->{$l2} =
                 [ sort keys %{$unified_info{$l1}->{$l2}} ];