meson: Make auto the default of the ssl option

The 'ssl' option is of type 'combo', but we add a choice 'auto' that
simulates the behavior of a feature option.  This way, openssl is used
automatically by default if present, but we retain the ability to
potentially select another ssl library.

Author: Nazir Bilal Yavuz <byavuz81@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/ad65ffd1-a9a7-fda1-59c6-f7dc763c3051%40enterprisedb.com

.cirrus.yml

@@ -181,7 +181,7 @@ task:
     su postgres <<-EOF
       meson setup \
         --buildtype=debug \
-        -Dcassert=true -Dssl=openssl -Duuid=bsd -Dtcl_version=tcl86 -Ddtrace=auto \
+        -Dcassert=true -Duuid=bsd -Dtcl_version=tcl86 -Ddtrace=auto \
         -DPG_TEST_EXTRA="$PG_TEST_EXTRA" \
         -Dextra_lib_dirs=/usr/local/lib -Dextra_include_dirs=/usr/local/include/ \
         build
@@ -243,7 +243,6 @@ LINUX_CONFIGURE_FEATURES: &LINUX_CONFIGURE_FEATURES >-
 
 LINUX_MESON_FEATURES: &LINUX_MESON_FEATURES >-
   -Dllvm=enabled
-  -Dssl=openssl
   -Duuid=e2fs
 
 
@@ -497,7 +496,7 @@ task:
       -Dextra_include_dirs=${brewpath}/include \
       -Dextra_lib_dirs=${brewpath}/lib \
       -Dcassert=true \
-      -Dssl=openssl -Duuid=e2fs -Ddtrace=auto \
+      -Duuid=e2fs -Ddtrace=auto \
       -Dsegsize_blocks=6 \
       -DPG_TEST_EXTRA="$PG_TEST_EXTRA" \
       build
@@ -568,7 +567,7 @@ task:
   # Use /DEBUG:FASTLINK to avoid high memory usage during linking
   configure_script: |
     vcvarsall x64
-    meson setup --backend ninja --buildtype debug -Dc_link_args=/DEBUG:FASTLINK -Dcassert=true -Db_pch=true -Dssl=openssl -Dextra_lib_dirs=c:\openssl\1.1\lib -Dextra_include_dirs=c:\openssl\1.1\include -DTAR=%TAR% -DPG_TEST_EXTRA="%PG_TEST_EXTRA%" build
+    meson setup --backend ninja --buildtype debug -Dc_link_args=/DEBUG:FASTLINK -Dcassert=true -Db_pch=true -Dextra_lib_dirs=c:\openssl\1.1\lib -Dextra_include_dirs=c:\openssl\1.1\include -DTAR=%TAR% -DPG_TEST_EXTRA="%PG_TEST_EXTRA%" build
 
   build_script: |
     vcvarsall x64

doc/src/sgml/installation.sgml

@@ -2474,7 +2474,7 @@ ninja install
      </varlistentry>
 
      <varlistentry id="configure-with-ssl-meson">
-      <term><option>-Dssl=<replaceable>LIBRARY</replaceable></option>
+      <term><option>-Dssl={ auto | <replaceable>LIBRARY</replaceable> }</option>
       <indexterm>
        <primary>OpenSSL</primary>
        <seealso>SSL</seealso>
@@ -2488,7 +2488,7 @@ ninja install
         <productname>OpenSSL</productname> package to be installed.  Building
         with this will check for the required header files and libraries to
         make sure that your <productname>OpenSSL</productname> installation is
-        sufficient before proceeding.  The default for this option is none.
+        sufficient before proceeding.  The default for this option is auto.
        </para>
       </listitem>
      </varlistentry>

meson.build

@@ -43,6 +43,7 @@ cc = meson.get_compiler('c')
 
 not_found_dep = dependency('', required: false)
 thread_dep = dependency('threads')
+auto_features = get_option('auto_features')
 
 
 
@@ -1171,7 +1172,16 @@ cdata.set('USE_SYSTEMD', systemd.found() ? 1 : false)
 # Library: SSL
 ###############################################################
 
-if get_option('ssl') == 'openssl'
+ssl = not_found_dep
+ssl_library = 'none'
+sslopt = get_option('ssl')
+
+if sslopt == 'auto' and auto_features.disabled()
+  sslopt = 'none'
+endif
+
+if sslopt in ['auto', 'openssl']
+  openssl_required = (sslopt == 'openssl')
 
   # Try to find openssl via pkg-config et al, if that doesn't work
   # (e.g. because it's provided as part of the OS, like on FreeBSD), look for
@@ -1193,13 +1203,12 @@ if get_option('ssl') == 'openssl'
 
     ssl = declare_dependency(dependencies: ssl_int,
                              include_directories: postgres_inc)
-  else
-    cc.has_header('openssl/ssl.h', args: test_c_args, dependencies: ssl, required: true)
-    cc.has_header('openssl/err.h', args: test_c_args, dependencies: ssl, required: true)
-
+  elif cc.has_header('openssl/ssl.h', args: test_c_args, dependencies: ssl, required: openssl_required) and \
+       cc.has_header('openssl/err.h', args: test_c_args, dependencies: ssl, required: openssl_required)
     ssl_int = [ssl]
   endif
 
+  if ssl.found()
     check_funcs = [
       ['CRYPTO_new_ex_data', {'required': true}],
       ['SSL_new', {'required': true}],
@@ -1228,24 +1237,37 @@ if get_option('ssl') == 'openssl'
       ['X509_get_signature_info'],
     ]
 
+    are_openssl_funcs_complete = true
     foreach c : check_funcs
       func = c.get(0)
       val = cc.has_function(func, args: test_c_args, dependencies: ssl_int)
       required = c.get(1, {}).get('required', false)
       if required and not val
+        are_openssl_funcs_complete = false
+        if openssl_required
           error('openssl function @0@ is required'.format(func))
+        endif
+        break
       elif not required
         cdata.set('HAVE_' + func.to_upper(), val ? 1 : false)
       endif
     endforeach
 
+    if are_openssl_funcs_complete
       cdata.set('USE_OPENSSL', 1,
                 description: 'Define to 1 to build with OpenSSL support. (-Dssl=openssl)')
       cdata.set('OPENSSL_API_COMPAT', '0x10001000L',
                 description: '''Define to the OpenSSL API version in use. This avoids deprecation warnings from newer OpenSSL versions.''')
+      ssl_library = 'openssl'
     else
       ssl = not_found_dep
     endif
+  endif
+endif
+
+if sslopt == 'auto' and auto_features.enabled() and not ssl.found()
+  error('no SSL library found')
+endif
 
 
 
@@ -3266,13 +3288,13 @@ if meson.version().version_compare('>=0.57')
       'llvm': llvm,
       'lz4': lz4,
       'nls': libintl,
+      'openssl': ssl,
       'pam': pam,
       'plperl': perl_dep,
       'plpython': python3_dep,
       'pltcl': tcl_dep,
       'readline': readline,
       'selinux': selinux,
-      'ssl': ssl,
       'systemd': systemd,
       'uuid': uuid,
       'zlib': zlib,

meson_options.txt

@@ -130,8 +130,8 @@ option('readline', type : 'feature', value : 'auto',
 option('selinux', type : 'feature', value : 'disabled',
   description: 'build with SELinux support')
 
-option('ssl', type : 'combo', choices : ['none', 'openssl'],
-  value : 'none',
+option('ssl', type : 'combo', choices : ['auto', 'none', 'openssl'],
+  value : 'auto',
   description: 'use LIB for SSL/TLS support (openssl)')
 
 option('systemd', type : 'feature', value: 'auto',

src/interfaces/libpq/meson.build

@@ -117,7 +117,7 @@ tests += {
       't/001_uri.pl',
       't/002_api.pl',
     ],
-    'env': {'with_ssl': get_option('ssl')},
+    'env': {'with_ssl': ssl_library},
   },
 }
 

src/makefiles/meson.build

@@ -66,7 +66,7 @@ pgxs_kv = {
   'SUN_STUDIO_CC': 'no', # not supported so far
 
   # want the chosen option, rather than the library
-  'with_ssl' : get_option('ssl'),
+  'with_ssl' : ssl_library,
   'with_uuid': uuidopt,
 
   'default_port': get_option('pgport'),

src/test/ssl/meson.build

@@ -6,7 +6,7 @@ tests += {
   'bd': meson.current_build_dir(),
   'tap': {
     'env': {
-      'with_ssl': get_option('ssl'),
+      'with_ssl': ssl_library,
       'OPENSSL': openssl.path(),
     },
     'tests': [