Configuration: produce include/openssl/configuration.h when configuring

The goal is to avoid having too much of the OpenSSL source rebuilt
because include/openssl/configuration.h, or even because it was a
Makefile target that was called upon (some make implementations
consider the use of a target as an update of that target, even if it
wasn't really updated).

To resolve this, we move the production of include/openssl/configuration.h
to configdata.pm, and only update it if there were any actual changes.

Fixes #16377

Reviewed-by: Tomas Mraz <tomas@openssl.org>
Reviewed-by: Todd Short <todd.short@me.com>
(Merged from https://github.com/openssl/openssl/pull/16378)

Configure

@@ -2854,8 +2854,11 @@ if (-f $configdata_outname) {
         # like nothing happened
         unlink "$configdata_outname.new";
 
-        # We still run configdata.pm if the build file (Makefile) is missing
-        $run_configdata = !( -f $target{build_file} );
+        # We still run configdata.pm if one of the build file (Makefile) or
+        # the configuration header file are missing
+        $run_configdata =
+            !( -f $target{build_file} )
+            || !( -f catfile('include', 'openssl', 'configuration.h') );
     }
 } else {
     $update_configdata = 1;

build.info

@@ -22,7 +22,6 @@ DEPEND[]=include/openssl/asn1.h \
          include/openssl/cmp.h \
          include/openssl/cms.h \
          include/openssl/conf.h \
-         include/openssl/configuration.h \
          include/openssl/crmf.h \
          include/openssl/crypto.h \
          include/openssl/ct.h \
@@ -49,7 +48,6 @@ GENERATE[include/openssl/bio.h]=include/openssl/bio.h.in
 GENERATE[include/openssl/cmp.h]=include/openssl/cmp.h.in
 GENERATE[include/openssl/cms.h]=include/openssl/cms.h.in
 GENERATE[include/openssl/conf.h]=include/openssl/conf.h.in
-GENERATE[include/openssl/configuration.h]=include/openssl/configuration.h.in
 GENERATE[include/openssl/crmf.h]=include/openssl/crmf.h.in
 GENERATE[include/openssl/crypto.h]=include/openssl/crypto.h.in
 GENERATE[include/openssl/ct.h]=include/openssl/ct.h.in

configdata.pm.in

@@ -77,6 +77,7 @@ unless (caller) {
     use Getopt::Long;
     use File::Spec::Functions;
     use File::Basename;
+    use File::Compare qw(compare_text);
     use File::Copy;
     use Pod::Usage;
 
@@ -131,10 +132,11 @@ use lib '{- $config{builddir} -}';
 use platform;
 _____
 
+        my $tmpl;
         open BUILDFILE, ">$buildfile.new"
             or die "Trying to create $buildfile.new: $!";
-        my $tmpl = OpenSSL::Template->new(TYPE => 'FILE',
-                                          SOURCE => $buildfile_template);
+        $tmpl = OpenSSL::Template->new(TYPE => 'FILE',
+                                       SOURCE => $buildfile_template);
         $tmpl->fill_in(FILENAME => $_,
                        OUTPUT => \*BUILDFILE,
                        HASH => \%gendata,
@@ -149,6 +151,56 @@ _____
             or die "Trying to rename $buildfile.new to $buildfile: $!";
         print 'Created ',$buildfile,"\n";
 
+        my $configuration_h =
+            catfile('include', 'openssl', 'configuration.h');
+        my $configuration_h_in =
+            catfile($config{sourcedir}, 'include', 'openssl', 'configuration.h.in');
+        open CONFIGURATION_H, ">${configuration_h}.new"
+            or die "Trying to create ${configuration_h}.new: $!";
+        $tmpl = OpenSSL::Template->new(TYPE => 'FILE',
+                                       SOURCE => $configuration_h_in);
+        $tmpl->fill_in(FILENAME => $_,
+                       OUTPUT => \*CONFIGURATION_H,
+                       HASH => \%gendata,
+                       PREPEND => $prepend,
+                       # To ensure that global variables and functions
+                       # defined in one template stick around for the
+                       # next, making them combinable
+                       PACKAGE => 'OpenSSL::safe')
+            or die $Text::Template::ERROR;
+        close CONFIGURATION_H;
+
+        # When using stat() on Windows, we can get it to perform better by
+        # avoid some data.  This doesn't affect the mtime field, so we're not
+        # losing anything...
+        ${^WIN32_SLOPPY_STAT} = 1;
+
+        my $update_configuration_h = 0;
+        if (-f $configuration_h) {
+            my $configuration_h_mtime = (stat($configuration_h))[9];
+            my $configuration_h_in_mtime = (stat($configuration_h_in))[9];
+
+            # If configuration.h.in was updated after the last configuration.h,
+            # or if configuration.h.new differs configuration.h, we update
+            # configuration.h
+            if ($configuration_h_mtime < $configuration_h_in_mtime
+                || compare_text("${configuration_h}.new", $configuration_h) != 0) {
+                $update_configuration_h = 1;
+            } else {
+                # If nothing has changed, let's just drop the new one and
+                # pretend like nothing happened
+                unlink "${configuration_h}.new"
+            }
+        } else {
+            $update_configuration_h = 1;
+        }
+
+        if ($update_configuration_h) {
+            rename("${configuration_h}.new", $configuration_h)
+                or die "Trying to rename ${configuration_h}.new to $configuration_h: $!";
+            print 'Created ',$configuration_h,"\n";
+        }
+
         exit(0);
     }