GNUStep runtime / libobjc2 build problems: tests failing or segfaulting

[Andreas Fink]

Hi all,

I'm trying to build gnustep base  with clang-7 on debian 9 and I constantly run into incompatibilities from the runtime or tests failing and I can't figure out the dependency issues here.

clang-7 comes from the clang repository

deb http://apt.llvm.org/stretch/ llvm-toolchain-stretch-7 main

deb-src http://apt.llvm.org/stretch/ llvm-toolchain-stretch-7 main

My gnustep make is configured like this:

export CC=/usr/bin/clang-7

export CXX=/usr/bin/clang++-7

export LD=/usr/bin/lld-7

export PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin

export PKG_CONFIG_PATH=/usr/local/lib/pkgconfig/

export RUNTIME_VERSION=gnustep-1.9

export OBJCFLAGS="-fblocks"

export CFLAGS="-L/usr/local/lib"

./configure \

            --with-layout=fhs \

            --disable-importing-config-file \

            --enable-native-objc-exceptions \

            --enable-objc-arc \

            --enable-install-ld-so-conf \

            --with-library-combo=ng-gnu-gnu \

            --with-config-file=/usr/local/etc/GNUstep/GNUstep.conf \

            --with-user-config-file='.GNUstep.conf' \

            --with-user-defaults-dir='GNUstep/Library/Defaults' \

            --with-objc-lib-flag="-l:libobjc.so.4.6" \

my libobjc2 is compiled like this:

    cmake .. -DCMAKE_C_COMPILER=/usr/bin/clang-7 -DCMAKE_CXX_COMPILER=/usr/bin/clang++-7  -DCMAKE_LINKER=/usr/bin/lld-7 -DCMAKE_BUILD_TYPE=RelWithDebInfo

and then when I compile gnustep-base

    export RUNTIME_VERSION=gnustep-1.9

    export OBJCFLAGS="-fblocks"

    export CFLAGS="-L/usr/local/lib"

    ./configure \

            --with-layout=fhs \

            --disable-importing-config-file \

            --enable-native-objc-exceptions \

            --enable-objc-arc \

            --enable-install-ld-so-conf \

            --with-library-combo=ng-gnu-gnu \

            --with-config-file=/usr/local/etc/GNUstep/GNUstep.conf \

            --with-user-config-file='.GNUstep.conf' \

            --with-user-defaults-dir='GNUstep/Library/Defaults' \

            --with-objc-lib-flag="-l:libobjc.so.4.6" \

I get this:

configure: error: Your compiler does not appear to implement the -fconstant-string-class option needed for support of strings.  Please check for a more recent version or consider using --enable-nxconstantstring

well clang-7 definitively does know -fconstant-string so this test is going nuts somehow.

I looked at the test  config/config.constant-string-class.m

and I figured out it segfaults:

# clang-7 -O0 -g config/config.constant-string-class.m -l:libobjc.so.4.6

In file included from config/config.constant-string-class.m:19:

config/objc-common.g:54:3: warning: assignment to Objective-C's isa is deprecated in favor of object_setClass() [-Wdeprecated-objc-isa-usage]

  obj->isa = self;

  ^  ~~~~~~~

  object_setClass( , )

config/objc-common.g:47:5: note: instance variable is declared here

 id isa;

    ^

config/objc-common.g:45:31: warning: class 'NSObject' defined without specifying a base class [-Wobjc-root-class]

GS_OBJC_ROOT_CLASS @interface NSObject

                              ^

config/objc-common.g:45:39: note: add a super class to fix this problem

GS_OBJC_ROOT_CLASS @interface NSObject

                                      ^

                                       : NSObject

config/config.constant-string-class.m:23:31: warning: class 'FooConstantString' defined without specifying a base class [-Wobjc-root-class]

GS_OBJC_ROOT_CLASS @interface FooConstantString

                              ^

config/config.constant-string-class.m:23:48: note: add a super class to fix this problem

GS_OBJC_ROOT_CLASS @interface FooConstantString

                                               ^

                                                : NSObject

config/config.constant-string-class.m:49:23: warning: incompatible pointer types initializing 'FooConstantString *' with an _expression_ of type 'NSString *'

      [-Wincompatible-pointer-types]

   FooConstantString *string = @"Antonio Valente";

                      ^        ~~~~~~~~~~~~~~~~~~

4 warnings generated.

[root@gnustep.fink-telecom.com base]# lldb ./a.out

(lldb) target create "./a.out"

Current executable set to './a.out' (x86_64).

(lldb) run

Process 15116 launched: '/Users/afink/development/gnustep/base/a.out' (x86_64)

Process 15116 stopped

* thread #1, name = 'a.out', stop reason = signal SIGSEGV: invalid address (fault address: 0x0)

    frame #0: 0x00007ffff7bcaae8 libobjc.so.4`___lldb_unnamed_symbol45$$libobjc.so.4 + 72

libobjc.so.4`___lldb_unnamed_symbol45$$libobjc.so.4:

->  0x7ffff7bcaae8 <+72>: movq   (%r12), %rax

    0x7ffff7bcaaec <+76>: movl   %eax, %ecx

    0x7ffff7bcaaee <+78>: movq   %rax, %rdx

    0x7ffff7bcaaf1 <+81>: shll   $0x5, %ecx

(lldb)

if I patch out the constant string test in configure.ac and rebuild it, then most gnustep-base test cases fail.

So I'm kind of lost on where the heck this comes from. I noticed in the past that my classes get referred to the wrong runtime version and thus access to members of superclasses returned wrong values which apparently depends on runtime version which is the reason why I want to recompile everything with a specific runtime version so we have 100% sure everything uses the same ABI. I only run my own code so I dont' need backwards compatibility.

Does anyone have a clue on how to fix this?