RFR: 8304871: Use default visibility for static library builds

[Severin Gehwolf]

On Mon, 27 Mar 2023 05:23:26 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Please review this change for symbol visibility of static library artefacts. This fixes an issue when
>> OpenJDK is being used as a base for generating native images preventing the symbols from being
>> exported and looked up from the executable. Note that symbol visibity is now controlled by a
>> linker version script downstream. This changes nothing for the regularly shipped dynamic libraries.
>> 
>> Thoughts?
>
> make/autoconf/flags-cflags.m4 line 639:
> 
>> 637:   STATIC_LIBS_CFLAGS="-DSTATIC_BUILD=1"
>> 638:   if test "x$TOOLCHAIN_TYPE" = xgcc || test "x$TOOLCHAIN_TYPE" = xclang; then
>> 639:     STATIC_LIBS_CFLAGS="$STATIC_LIBS_CFLAGS -ffunction-sections -fdata-sections"
> 
> Is it better/clearer to make the use of the default explicit as we do in the source:
> 
> #define JNIEXPORT     __attribute__((visibility("default")))
> 
> ?

@dholmes-ora Do you mean something like this (instead of removing the `-D` expression)?


STATIC_LIBS_CFLAGS="$STATIC_LIBS_CFLAGS -ffunction-sections -fdata-sections \
      -DJNIEXPORT='__attribute__((visibility("default")))'"


I can surely do that if that's preferred. No preference either way as far as I'm concerned.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13177#discussion_r1149000471