Re: [Qemu-devel] [RFC 41/48] configure: add --enable-plugins

[Emilio G. Cota]

On Tue, Nov 27, 2018 at 15:43:52 +0300, Roman Bolshakov wrote:
> ld64 on macOS has similar -exported_symbols_list option. Here's the reference:
> 
>      -exported_symbols_list filename
>       The specified filename contains a list of global symbol names
>       that will remain as global symbols in the output file.  All other
>       global symbols will be treated as if they were marked as
>       __private_extern__ (aka visibility=hidden) and will not be global in
>       the output file. The symbol names listed in filename must be one per
>       line.  Leading and trailing white space are not part of the symbol
>       name.  Lines starting with # are ignored, as are lines with only white
>       space.  Some wildcards (similar to shell file matching) are supported.
>       The * matches zero or more characters.  The ?  matches one character.
>       [abc] matches one character which must be an 'a', 'b', or 'c'.
>       [a-z] matches any single lower case letter from 'a' to 'z'.
> 
> 
> I can try your branch if you add support of the linker flag or send required
> changes via GitHub.

Can you please try this branch? I added a commit with the appended.
  https://github.com/cota/qemu/tree/plugin-v2

You can inspect the symbols in the final binary with
`readelf --dyn-syms' or `nm -D'.

Thanks,

                Emilio

---
diff --git a/configure b/configure
index fe9707d951..3dc9c9697b 100755
--- a/configure
+++ b/configure
@@ -5176,15 +5176,31 @@ int main(void)
 }
 EOF
 
+ld_dynamic_list="no"
 if compile_prog "" "-Wl,--dynamic-list=$TMPTXT" ; then
   ld_dynamic_list="yes"
-else
-  if test "$plugins" = "yes" ; then
-    error_exit \
-        "Plugin support requires specifying a set of symbols that " \
-        "are exported to plugins. Unfortunately your linker doesn't " \
-        "support the flag (--dynamic-list) used for this purpose."
-  fi
+fi
+
+#########################################
+# See if -exported_symbols_list is supported by the linker
+
+cat > $TMPTXT <<EOF
+  foo
+EOF
+
+ld_exported_symbols_list="no"
+if compile_prog "" "-Wl,-exported_symbols_list,$TMPTXT" ; then
+  ld_exported_symbols_list="yes"
+fi
+
+if  test "$plugins" = "yes" &&
+    test "$ld_dynamic_list" = "no" &&
+    test "$ld_exported_symbols_list" = "no" ; then
+  error_exit \
+      "Plugin support requires specifying a set of symbols that " \
+      "are exported to plugins. Unfortunately your linker doesn't " \
+      "support the flag (--dynamic-list or -exported_symbols_list) used " \
+      "for this purpose."
 fi
 
 ########################################
@@ -6827,7 +6843,18 @@ fi
 if test "$plugins" = "yes" ; then
     echo "CONFIG_PLUGINS=y" >> $config_host_mak
     LIBS="-ldl $LIBS"
-    LDFLAGS="-Wl,--dynamic-list=\$(SRC_PATH)/qemu-plugins.symbols $LDFLAGS"
+    if test "$ld_dynamic_list" = "yes" ; then
+       LDFLAGS="-Wl,--dynamic-list=\$(SRC_PATH)/qemu-plugins.symbols $LDFLAGS"
+    elif test "$ld_exported_symbols_list" = "yes" ; then
+       ld64_symbols=qemu-plugins-ld64.symbols
+       echo "# Automatically generated by configure - do not modify" > 
$ld64_symbols
+       cat "$source_path/qemu-plugins.symbols" | grep qemu_ | sed 's/;//g' >> 
$ld64_symbols
+       LDFLAGS="-Wl,-exported_symbols_list,\$(BUILD_DIR)/$ld64_symbols 
$LDFLAGS"
+    else
+       error_exit \
+           "If \$plugins=yes, either \$ld_dynamic_list or " \
+           "\$ld_exported_symbols_list should have been set to 'yes'."
+    fi
 fi
 
 if test "$tcg_interpreter" = "yes"; then