Bug#1142751: bazel-bootstrap: 32 bit support

[Ying-Chun Liu (PaulLiu)]

Hi all,






## Heap size

First, in debian/rules








BAZEL_JAVAC_OPTS = --add-opens=java.base/java.nio=ALL-UNNAMED \
                   --add-opens=java.base/java.lang=ALL-UNNAMED \
                   -proc:full \
                   -Acom.google.auto.value.AutoBuilderIsUnstable
ifeq ($(DEB_HOST_ARCH_BITS),32)
    export BAZEL_JAVAC_OPTS := -J-Xmx1536m $(BAZEL_JAVAC_OPTS)
else
    export BAZEL_JAVAC_OPTS := -J-Xmx4096m $(BAZEL_JAVAC_OPTS)
endif


## mmap

And then we will met the following error

In src/tools/singlejar/mapped_file_posix.inc


// The implementation is specific to 64-bit Linux / OS X / BSD.
#if !((defined(__linux__) || defined(__APPLE__) || defined(__FreeBSD__) || \
       defined(__OpenBSD__)) &&                 \
      __SIZEOF_POINTER__ == 8)
#error This code for 64 bit Unix.
#endif





## bazel rules

And then we will meet the most uncomfortable issues here.

rules-java will be fail because it cannot find jni_md.h.





For i386 and armhf, we might need to go through the same procedure again.


Yours,

Paul

I've been research this for a while. I remove architecture-is-64-bit in Build-Depends and build it in i386 environment. And now I know why it is not working. export BAZEL_JAVAC_OPTS = -J-Xmx4096m --add-opens=java.base/java.nio=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED -proc:full -Acom.google.auto.value.AutoBuilderIsUnstable causes failure because -Xmx4096m is too large for 32-bit platforms. Because on 32-bit platform the memory address is only 4GB. So e can change it to This is because in bazel it uses mmap to map file to memory. And if it maps some files larger than 4GB, we will have some problems here. But it is ok if we add (__SIZEOF_POINTER__ == 8 || __SIZEOF_POINTER__ == 4) to just let it pass. And this is just caused by those bazel rules. Based on how we add loongson support, that means we might look into bazel-rules-cc, bazel-rules-java and bazel-platforms. Previously Dandan Zhang make a patch for bazel-bootstrap to support loong64 when we were at version 4. But that patch has been splitted to 4. And applied to bazel-bootstrap, bazel-rules-cc, bazel-rules-java and bazel-platforms. It seems that we have to do this again. And if we look at the upstream, the mainline, it seems to me that we have some technical debt there for loong64. We might need to submit these patches first to the upstream.

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