Re: Build failure "/mnt/data/home/software/openjdk/src/hotspot/share/gc/parallel/objectStartArray.cpp:106:56: error: ‘void* memset(void*, int, size_t)’ writing to an object of type ‘class HeapWord’ with ‘private’ member ‘HeapWord::i’ [-Werror=class-memacc

[Magnus Ihse Bursie]

On 2018-12-31 23:15, Karl-Philipp Richter wrote:
> Hi Andrew,
> Thanks for your quick reply.
>
> Am 31.12.18 um 21:08 schrieb Andrew Luo:
>> Can you run gcc --version and tell us the version of GCC that you are using?
> My version is gcc (Ubuntu 8.2.0-7ubuntu1) 8.2.0.
>
>> I'm guessing this was added in a newer version of GCC (class-memaccess was added in GCC 8), and can probably be worked around using -Wno-error=class-memaccess.  That's not saying I don't think we should fix this, just suggesting a workaround for now if you want to compile on GCC 8 before this is fixed.  Although I believe that per the C++ standard you are allowed to memcpy/memset trivial classes (clang only warns on non-trivial classes: https://reviews.llvm.org/D45310) so GCC's warning seems to be a bit too broad.
> `env MAKEFLAGS= bash ./configure
> --with-extra-cflags=-Wno-error=class-memaccess
> --with-extra-cxxflags=-Wno-error=class-memaccess && make` avoid the
> build failure, however the build now fails because of
>
> ```
> /mnt/data/home/software/openjdk/src/java.base/unix/native/libjli/java_md_solinux.c:
> In function ‘ContinueInNewThread0’:
> /mnt/data/home/software/openjdk/src/java.base/unix/native/libjli/java_md_solinux.c:747:37:
> error: cast between incompatible function types from ‘int (*)(void *)’
> to ‘void * (*)(void *)’ [-Werror=cast-function-type]
>       if (pthread_create(&tid, &attr, (void *(*)(void*))continuation,
> (void*)args) == 0) {
>                                       ^
> cc1: all warnings being treated as errors
> make[3]: *** [CoreLibraries.gmk:212:
> /mnt/data/home/software/openjdk/build/linux-x86_64-server-release/support/native/java.base/libjli/java_md_solinux.o]
> Fehler 1
> make[3]: *** Auf noch nicht beendete Prozesse wird gewartet …
> make[2]: *** [make/Main.gmk:215: java.base-libs] Fehler 2
>
> ERROR: Build failed for target 'default (exploded-image)' in
> configuration 'linux-x86_64-server-release' (exit code 2)
> ```
>
> I agree that the issue should be fixed.
>
> Since Ubuntu is not among the least popular Linux distributions, I
> recommend a review of your continuous integration system which might
> need to include more systems. The setup on GitLab is an example to
> perform these tests easily, but you probably already have already a CI
> set up which you can extend.
>
> Since I don't need to build OpenJDK urgently, I'd rather see these build
> issues detected and fixed by CI coverage of the build process than
> stumbling from one to another - it's probably only these two, but afaik
> that's a lot of a widely use operating system.

The default behavior of the build system is to compile with warnings as 
errors. When your build fails, the very last message printed by the 
build system is:
"Hint: See doc/building.html#troubleshooting for assistance."

If you follow the instructions, you will find this paragraph: [1]

"By default, the JDK has a strict approach where warnings from the 
compiler is considered errors which fail the build. For very new or very 
old compiler versions, this can trigger new classes of warnings, which 
thus fails the build. Run configure with --disable-warnings-as-errors to 
turn of this behavior. (The warnings will still show, but not make the 
build fail.)"

Trying to build a system as complex as OpenJDK without reading the 
documentation is a very optimistic approach.

/Magnus

[1] 
http://hg.openjdk.java.net/jdk/jdk/raw-file/tip/doc/building.html#troubleshooting





>
>> Are you interested in contributing a fix to this as well - if not I can work on this later this week as well.
> I have not enough knowledge to provide a good fix.
>
>> (By the way, your link https://gitlab.com/krichter/openjdk/-/jobs/140219987 requires signing in).
> My bad, fixed.
>
> -Kalle
>