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Hi Antoni,<br>
<br>
This discussion belongs in build-dev mailing list.<br>
<br>
-- <br>
Regards,<br>
Alexey<br>
<br>
<div class="moz-cite-prefix">On 2025-12-17 11:22, Antoni Jankowski
wrote:<br>
</div>
<blockquote type="cite" cite="mid:CAM4sPk-53EY=HqyfxVL7Z2vLjvss-2jeBROPrh=GeQfWT8zAHw@mail.gmail.com">
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<div>Hi, </div>
<div><br>
</div>
<div>I've recently studied the jdk21u build system and noticed
that at its core it is not meant to handle BUILDJDK and
TARGETJDK being made for two very different systems. </div>
<div>Many of the FLAGS are shared between the two and in many
cases that may be problematic. A good example is the
GENDEPS_FLAGS variable, which is only present in one
version, just in the <i>make/autoconf/<a href="http://spec.gmk.in" target="_blank" moz-do-not-send="true">spec.gmk.in</a></i>, meaning that
the BUILDJDK gets the same GENDEPS_FLAGS as the TARGETJDK.
Shouldn't this variable be split into GENDEPS_FLAGS_TARGET
and GENDEPS_FLAGS_BUILD to ensure a correct generation of
dependency files in all sorts of cross-compilation
scenarios?</div>
<div><br>
</div>
<div>Same story is with the variables defined in <i>make/autoconf/flags-cflags.m4,
make/autoconf/flags-ldflags.m4 and
make/autoconf/flags-other.m4, </i>like<br>
* $2CFLAGS_JDKEXE</div>
<div>* $2CXXFLAGS_JDKEXE</div>
<div>* $2CFLAGS_JDKLIB</div>
<div>as they all depend on the OPENJDK_TARGET_OS variable,
which is the same for both TARGETJDK and BUILDJDK. I suppose
the root of the problem is right there, where in <i><a href="http://build-spec.gmk.in" target="_blank" moz-do-not-send="true">build-spec.gmk.in</a></i> the
OPENJDK_TARGET_OS variable is not overwritten with the value
of OPENJDK_BUILD_OS, like it's done with other
OPENJDK_TARGET_* variables. I suppose no problems occur when
the compiler is shared between the target and the build
platforms, even less problems in case of linux or macOS in
both cases being the operating system, however in case of
the target system differing greatly from the build, the
cross-compilation is close to impossible with the current
build system.</div>
<div><br>
</div>
<div>I wonder if that is a design choice, or perhaps a
limitation that was not planned.</div>
<div>Would you be open for changes that make it a bit easier
to introduce a new platform target to <span class="gmail-il">openjdk</span>? I'd gladly post a pull
request solving the issues mentioned.</div>
<div><br>
</div>
<div>Best regards,</div>
<div>Antoni Jankowski</div>
</div>
</div>
</blockquote>
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