RFR: 8351322: Parameterize link option for pthreads

[Erik Joelsson]

On Thu, 6 Mar 2025 10:39:27 GMT, snake66 <duke at openjdk.org> wrote:

> Replace hardcoded instances of `-lpthread` with `$(LIBPTHREAD)`, so that it's possible to parameterize this for platforms that use different flags for enabling posix threads.
> 
> This work is a continuation of the work done by Greg Lewis in [1], but generalized for the full JDK, and set at the configure stage.
> 
> Sponsored by: The FreeBSD Foundation
> Co-authored-by: Greg Lewis <glewis at eyesbeyond.com>
> 
> [1]: https://github.com/battleblow/jdk23u/commit/dbd90aa8ab0b7f5e4865864a7c63d975daacabf4

What is the intended way of using this? Do you run make with `LIBPTHREAD=-pthread` or do you apply a patch on `libraries.m4` for the specific way of linking to pthread?

make/autoconf/libraries.m4 line 142:

> 140:   # Threading library
> 141:   if test "x$OPENJDK_TARGET_OS" = xlinux || test "x$OPENJDK_TARGET_OS" = xaix; then
> 142:     BASIC_JVM_LIBS="$BASIC_JVM_LIBS $(LIBPTHREAD)"

If you specifically need this to be resolved in the makefile rather than here, then please add a comment explaining why, otherwise use a shell script variable reference.

Suggestion:

    BASIC_JVM_LIBS="$BASIC_JVM_LIBS $LIBPTHREAD"

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PR Review: https://git.openjdk.org/jdk/pull/23930#pullrequestreview-2664582520
PR Review Comment: https://git.openjdk.org/jdk/pull/23930#discussion_r1983435650