Re: [PATCH] {compilers-for-testsuite} readme: how to run the testsuite with cross-compilers

[Peter Rosin]

Stefano Lattarini skrev 2011-12-20 12:13:
> * tests/README: Suggest a better way to run the automake testsuite
> with cross-compilers -- that is, configuring the Automake source
> tree with proper `--build' and `--host' configure option.  And
> yes, specifying both these options (not only `--host') is indeed
> required to avoid spurious failures in corner cases.
> When you call configure with the `--host' option but without the
> `--build' option, configure tries to auto-detect whether you are
> cross-compiling or not, by trying to run a generated executable.
> That test might spuriously "succeed" in some corner cases (e.g.,
> Cygwin is able to run non-Cygwin apps).  In fact, generally, it
> can be the case that a cross-compilation is not detected as a
> cross anymore just because someone has installed an emulator; as
> an example, think of what can happen on a GNU/Linux system that
> is configured (through the use of the binfmt_misc kernel module)
> to execute PE executables (compiled for MS-DOS or Windows) through
> Wine *automatically*.  In conclusion, configure needs to be used
> as recommended in the documentation (i.e., by specifying *both*
> `--host' and `--build' instead of just one of them) to not have
> the build fall into any of a number of weird traps.
> * tests/defs (cross_compiling): Improve comments.
> ---
>  ChangeLog    |   25 +++++++++++++++++++++++++
>  tests/README |   24 ++++++++++++------------
>  tests/defs   |    7 +++++++
>  3 files changed, 44 insertions(+), 12 deletions(-)
> 
> diff --git a/ChangeLog b/ChangeLog
> index bb741bb..05ef6b8 100644
> --- a/ChangeLog
> +++ b/ChangeLog
> @@ -1,3 +1,28 @@
> +2011-12-20  Stefano Lattarini  <address@hidden>
> +         Peter Rosin  <address@hidden>
> +
> +     readme: how to run the testsuite with cross-compilers
> +     * tests/README: Suggest a better way to run the automake testsuite
> +     with cross-compilers -- that is, configuring the Automake source
> +     tree with proper `--build' and `--host' configure option.  And
> +     yes, specifying both these options (not only `--host') is indeed
> +     required to avoid spurious failures in corner cases.
> +     When you call configure with the `--host' option but without the
> +     `--build' option, configure tries to auto-detect whether you are
> +     cross-compiling or not, by trying to run a generated executable.
> +     That test might spuriously "succeed" in some corner cases (e.g.,
> +     Cygwin is able to run non-Cygwin apps).  In fact, generally, it
> +     can be the case that a cross-compilation is not detected as a
> +     cross anymore just because someone has installed an emulator; as
> +     an example, think of what can happen on a GNU/Linux system that
> +     is configured (through the use of the binfmt_misc kernel module)
> +     to execute PE executables (compiled for MS-DOS or Windows) through
> +     Wine *automatically*.  In conclusion, configure needs to be used
> +     as recommended in the documentation (i.e., by specifying *both*
> +     `--host' and `--build' instead of just one of them) to not have
> +     the build fall into any of a number of weird traps.
> +     * tests/defs (cross_compiling): Improve comments.
> +
>  2011-10-25  Stefano Lattarini  <address@hidden>
>  
>       tests: no need to unset CFLAGS in tests requiring 'gcc' anymore
> diff --git a/tests/README b/tests/README
> index 980299d..4d7f21d 100644
> --- a/tests/README
> +++ b/tests/README
> @@ -29,18 +29,18 @@ Running the tests
>      make -k check TESTS="foo.test bar.test"             (GNU make)
>      env TESTS="foo.test bar.test" make -e -k check      (non-GNU make)
>  
> - To run the tests in cross-compilation mode:
> -
> -    make -k check host_alias="$host_alias"              (GNU make)
> -    env host_alias="$host_alias" make -e -k check       (non-GNU make)
> -
> - Here `$host_alias' should be defined to a proper value different from
> - configure-determined `$build_alias', and should refer to a set of
> - cross-compilers you have available on your system; for example, if
> - on Linux you have a set of MinGW-targeted cross-compilers named
> - 'i586-mingw32msvc-cc', 'i586-mingw32msvc-c++', etc., you could use:
> -
> -   make -k check host_alias='i586-mingw32msvc'
> + To run the tests in cross-compilation mode, you should first configure
> + the automake source tree to a cross-compilation setup.  For example, to
> + run with a Linux-to-Cygwin cross compiler, you will need something like

I think you mean Linux-to-MinGW here, Linux-to-Cygwin is not as common...

> + this:
> +
> +   ./configure --host i586-mingw32msvc --build i686-pc-linux-gnu

...and this is the proof. :-)

Still, RMS might want you to say GNU/Linux-to-MinGW. Your call!

> + To avoid possible spurious error, you really have to *explicitly* specify
> + `--build' in addition to `--host'; the `lib/config.guess' script can help
> + you in determining what is the correct value you should pass to `--build'.

I would write the last part of the above like this:

the `lib/config.guess' script can help determine the correct value to pass
to `--build'.

> + Then you can just run the testsuite in the usual way, and the test cases
> + using a compiler should automatically use a cross-compilation setup.
>  
>  
>  Interpretation
> diff --git a/tests/defs b/tests/defs
> index 1a9ba37..ac2ebd4 100644
> --- a/tests/defs
> +++ b/tests/defs
> @@ -228,6 +228,13 @@ diag_string_="#%#"
>  # tests (or portions of them) that requires a native compiler.
>  cross_compiling ()
>  {
> +  # Quoting from the autoconf manual:
> +  #   ... [$host_alias and $build both] default to the result of running
> +  #   config.guess, unless you specify either --build or --host.  In
> +  #   this case, the default becomes the system type you specified.
> +  #   If you specify both, *and they're different*, configure enters
> +  #   cross compilation mode (so it doesn't run any tests that require
> +  #   execution).
>    test x"$host_alias" != x && test x"$build_alias" != x"$host_alias"
>  }
>  

Cheers,
Peter