37 lines
1.5 KiB
Markdown
37 lines
1.5 KiB
Markdown
## Bootstrapping OpenJDK 8
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```sh
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# If you are on arm64, you first need to unmask app-arch/fastjar
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sudo emerge -a1v =dev-java/icedtea-3.7.0
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sudo emerge -av dev-java/openjdk:8
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sudo emerge -a --depclean # Remove old software that was used for bootstrapping
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```
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Note: you need to do it in two steps as currently ant-core:bootstrap is not co-installable
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with ant-core:0 from the Gentoo tree.
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## Bootstrapping OpenJDK 11
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```sh
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sudo emerge -a1v =dev-java/openjdk-11.0.5_p10
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```
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At this point you can remove this overlay and install OpenJDK from main tree:
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```sh
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sudo emerge -a dev-java/openjdk:11
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```
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## Bootstrapping story
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We first compile fastjar and jikes java compiler both of which are written in C++.
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This is enough to compile an old version of GNU Classpath 0.93. Then we compile an old
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version of JamVM 1.5.1. This serves as our initial Java Runtime Environment.
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We use this to compile ant 1.8.1 which then allows us to build ecj-3.2. This allows us
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to compile GNU Classpath 0.99 which comes with more java tools (e.g. javah). Then we
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compile JamVM 2.0.0. This serves as our second Java environment.
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Finally, we compile git snapshot of GNU Classpath which has a much better support for Java 1.6.
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Then we compile a slightly patched ecj-4.2. Together with JamVM 2.0.0 this will serve as
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Java environment that can bootstrap Icedtea 2 (Java 7). Unfortunately, I was only able to build
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Java 7 with JamVM as VM (which is slower), Hotspot build failed. JamVM with OpenJDK 7 classes
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can build Icedtea 3 with Hotspot VM.
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