clang 22 libs-base configure step fails on Linux

[mcarans]

The GitHub Actions job for the Arch Linux Oolite build failed at the configure step when building GNUstep base:

 clang-22.1.1-1-x86_64 downloading...
 llvm-libs-22.1.1-1-x86_64 downloading...
 compiler-rt-22.1.1-1-x86_64 downloading...
 libedit-20251016_3.1-1-x86_64 downloading...
...
checking whether objc really works... yes
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
checking if the compiler supports -fconstant-string-class... no

The previous successful run shows that the only change is the clang version:

 clang-21.1.8-1-x86_64 downloading...
 llvm-libs-21.1.8-1-x86_64 downloading...
 compiler-rt-21.1.8-2-x86_64 downloading...
 libedit-20251016_3.1-1-x86_64 downloading...
...
checking whether objc really works... yes
checking if the compiler supports -fconstant-string-class... yes

Here is how I build libobjc2, tools-make and libs-base:

    cd libobjc2
    rm -rf build
    mkdir build
    cd build
    if ! cmake -DTESTS=on -DCMAKE_BUILD_TYPE=Release -DGNUSTEP_INSTALL_TYPE=NONE -DEMBEDDED_BLOCKS_RUNTIME=ON -DOLDABI_COMPAT=OFF ../; then
        echo "❌ libobjc2 cmake configure failed!" >&2
        return 1
    fi

    if ! cmake --build .; then
        echo "❌ libobjc2 cmake build failed!" >&2
        return 1
    fi
    cmake --install .
    cd ../..

    cd tools-make
    make clean

    if [[ ${CURRENT_DISTRO,,} == "redhat" ]]; then
        LIB_PARAM="--with-libdir=lib64"
    else
        LIB_PARAM=""
    fi

    if ! ./configure --with-library-combo=ng-gnu-gnu --with-runtime-abi=gnustep-2.2 ${LIB_PARAM:+"$LIB_PARAM"}; then
        echo "❌ tools-make configure failed!" >&2
        return 1
    fi
    make
    make install
    cd ..

    cd libs-base
    make clean
    source /usr/local/share/GNUstep/Makefiles/GNUstep.sh
    if ! ./configure; then
        echo "❌ libs-base configure failed!" >&2
        return 1
    fi
    if ! make -j$(nproc); then
        echo "❌ libs-base make failed!" >&2
        return 1
    fi
    make install

Is this failure a bug or do I need to change something in how I build GNUstep with clang 22?

[LW-archlinux]

The error also occurs when building gnustep-base 1.31.1 .
clang version is 22.1.1

[pkgdemon]

@rfm For what it is worth I also noticed this with Gershwin for CI jobs we had to build on Arch Linux and make ISOs. Debian, FreeBSD with older clang do still build fine, but I have not been able to work around Arch failing.

[rfm]

I'm away until next weekend, so can't look into this for a while. However, you may be able to see the cause if the problem in the log file (config.log). If there is a bug/change-of-behavior in clang, it's likely going to have provided error messages which may hint at how to work around it.

[mcarans]

@rfm I attach config.log

config.log

I think the relevant bit of config.log is this:

configure:9028: clang -o conftest -g -O2  -I/usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include  -x objective-c -fconstant-string-class=FooConstantString  -L/usr/local/lib -L/usr/local/lib -L/usr/local/lib -L/usr/local/lib conftest.c -lrt -ldl  -lresolv -lpthread -pthread -fexceptions -rdynamic -fobjc-runtime=gnustep-2.2 -fblocks -L/home/mcarans/GNUstep/Library/Libraries -L/usr/local/lib -lpthread -lobjc -lm   -lpthread  >&5
In file included from conftest.c:125:
In file included from ././config/config.constant-string-class.m:20:
././config/objc-common.g:54:3: warning: assignment to Objective-C's isa is deprecated in favor of object_setClass() [-Wdeprecated-objc-isa-usage]
   54 |   obj->isa = self;
      |   ^  ~~~~~~~     
      |   object_setClass( , )
././config/objc-common.g:47:5: note: instance variable is declared here
   47 |  id isa;
      |     ^
In file included from conftest.c:125:
././config/config.constant-string-class.m:56:12: warning: returning 'const char *const' from a function with result type 'char *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
   56 |     return c_string;
      |            ^~~~~~~~
././config/config.constant-string-class.m:64:23: error: incompatible pointer types initializing 'FooConstantString *' with an expression of type 'NSString *' [-Wincompatible-pointer-types]
   64 |    FooConstantString *string = @"Antonio Valente";
      |                       ^        ~~~~~~~~~~~~~~~~~~
2 warnings and 1 error generated.
configure:9028: $? = 1
configure: program exited with status 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| #define OPTION_NO_ENVIRONMENT 0
| #define GNUSTEP_TARGET_MAKEFILES "/usr/local/share/GNUstep/Makefiles"
| #define GNUSTEP_TARGET_USER_DEFAULTS_DIR "GNUstep/Defaults"
| #define GNUSTEP_TARGET_USER_CONFIG_FILE ".GNUstep.conf"
| #define GNUSTEP_TARGET_CONFIG_FILE "/usr/local/etc/GNUstep/GNUstep.conf"
| #define GNUSTEP_TARGET_SYSTEM_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_SYSTEM_ADMIN_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_SYSTEM_WEB_APPS "/usr/local/lib/GNUstep/WebApplications"
| #define GNUSTEP_TARGET_SYSTEM_TOOLS "/usr/local/bin"
| #define GNUSTEP_TARGET_SYSTEM_ADMIN_TOOLS "/usr/local/sbin"
| #define GNUSTEP_TARGET_SYSTEM_LIBRARY "/usr/local/lib/GNUstep"
| #define GNUSTEP_TARGET_SYSTEM_LIBRARIES "/usr/local/lib"
| #define GNUSTEP_TARGET_SYSTEM_SERVICES "/usr/local/lib/GNUstep/Services"
| #define GNUSTEP_TARGET_SYSTEM_HEADERS "/usr/local/include"
| #define GNUSTEP_TARGET_SYSTEM_DOC "/usr/local/share/GNUstep/Documentation"
| #define GNUSTEP_TARGET_SYSTEM_DOC_MAN "/usr/local/share/man"
| #define GNUSTEP_TARGET_SYSTEM_DOC_INFO "/usr/local/share/info"
| #define GNUSTEP_TARGET_NETWORK_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_NETWORK_ADMIN_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_NETWORK_WEB_APPS "/usr/local/lib/GNUstep/WebApplications"
| #define GNUSTEP_TARGET_NETWORK_TOOLS "/usr/local/bin"
| #define GNUSTEP_TARGET_NETWORK_ADMIN_TOOLS "/usr/local/sbin"
| #define GNUSTEP_TARGET_NETWORK_LIBRARY "/usr/local/lib/GNUstep"
| #define GNUSTEP_TARGET_NETWORK_LIBRARIES "/usr/local/lib"
| #define GNUSTEP_TARGET_NETWORK_SERVICES "/usr/local/lib/GNUstep/Services"
| #define GNUSTEP_TARGET_NETWORK_HEADERS "/usr/local/include"
| #define GNUSTEP_TARGET_NETWORK_DOC "/usr/local/share/GNUstep/Documentation"
| #define GNUSTEP_TARGET_NETWORK_DOC_MAN "/usr/local/share/man"
| #define GNUSTEP_TARGET_NETWORK_DOC_INFO "/usr/local/share/info"
| #define GNUSTEP_TARGET_LOCAL_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_LOCAL_ADMIN_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_LOCAL_WEB_APPS "/usr/local/lib/GNUstep/WebApplications"
| #define GNUSTEP_TARGET_LOCAL_TOOLS "/usr/local/bin"
| #define GNUSTEP_TARGET_LOCAL_ADMIN_TOOLS "/usr/local/sbin"
| #define GNUSTEP_TARGET_LOCAL_LIBRARY "/usr/local/lib/GNUstep"
| #define GNUSTEP_TARGET_LOCAL_LIBRARIES "/usr/local/lib"
| #define GNUSTEP_TARGET_LOCAL_SERVICES "/usr/local/lib/GNUstep/Services"
| #define GNUSTEP_TARGET_LOCAL_HEADERS "/usr/local/include"
| #define GNUSTEP_TARGET_LOCAL_DOC "/usr/local/share/GNUstep/Documentation"
| #define GNUSTEP_TARGET_LOCAL_DOC_MAN "/usr/local/share/man"
| #define GNUSTEP_TARGET_LOCAL_DOC_INFO "/usr/local/share/info"
| #define GNUSTEP_TARGET_USER_DIR_APPS "GNUstep/Applications"
| #define GNUSTEP_TARGET_USER_DIR_ADMIN_APPS "GNUstep/Applications/Admin"
| #define GNUSTEP_TARGET_USER_DIR_WEB_APPS "GNUstep/WebApplications"
| #define GNUSTEP_TARGET_USER_DIR_TOOLS "GNUstep/Tools"
| #define GNUSTEP_TARGET_USER_DIR_ADMIN_TOOLS "GNUstep/Tools/Admin"
| #define GNUSTEP_TARGET_USER_DIR_LIBRARY "GNUstep/Library"
| #define GNUSTEP_TARGET_USER_DIR_LIBRARIES "GNUstep/Library/Libraries"
| #define GNUSTEP_TARGET_USER_DIR_SERVICES "/Services"
| #define GNUSTEP_TARGET_USER_DIR_HEADERS "GNUstep/Library/Headers"
| #define GNUSTEP_TARGET_USER_DIR_DOC "GNUstep/Library/Documentation"
| #define GNUSTEP_TARGET_USER_DIR_DOC_MAN "GNUstep/Library/Documentation/man"
| #define GNUSTEP_TARGET_USER_DIR_DOC_INFO "GNUstep/Library/Documentation/info"
| #define GNUSTEP_TARGET_SYSTEM_USERS_DIR ""
| #define GNUSTEP_TARGET_NETWORK_USERS_DIR ""
| #define GNUSTEP_TARGET_LOCAL_USERS_DIR ""
| #define HAVE_STDIO_H 1
| #define HAVE_STDLIB_H 1
| #define HAVE_STRING_H 1
| #define HAVE_INTTYPES_H 1
| #define HAVE_STDINT_H 1
| #define HAVE_STRINGS_H 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_SYS_TYPES_H 1
| #define HAVE_UNISTD_H 1
| #define HAVE_WCHAR_H 1
| #define STDC_HEADERS 1
| #define _ALL_SOURCE 1
| #define _DARWIN_C_SOURCE 1
| #define _GNU_SOURCE 1
| #define _HPUX_ALT_XOPEN_SOCKET_API 1
| #define _NETBSD_SOURCE 1
| #define _OPENBSD_SOURCE 1
| #define _POSIX_PTHREAD_SEMANTICS 1
| #define __STDC_WANT_IEC_60559_ATTRIBS_EXT__ 1
| #define __STDC_WANT_IEC_60559_BFP_EXT__ 1
| #define __STDC_WANT_IEC_60559_DFP_EXT__ 1
| #define __STDC_WANT_IEC_60559_FUNCS_EXT__ 1
| #define __STDC_WANT_IEC_60559_TYPES_EXT__ 1
| #define __STDC_WANT_LIB_EXT2__ 1
| #define __STDC_WANT_MATH_SPEC_FUNCS__ 1
| #define _TANDEM_SOURCE 1
| #define __EXTENSIONS__ 1
| #define HAVE_FSEEKO 1
| #define USE_ATOMIC_BUILTINS 1
| #define HAVE_OBJC_RUNTIME_H 1
| #define HAVE_OBJC_OBJC_H 1
| #define HAVE_VISIBILITY_ATTRIBUTE 1
| #define SIZEOF_VOIDP 8
| #define SIZEOF_SHORT 2
| #define SIZEOF_INT 4
| #define SIZEOF_LONG 8
| #define SIZEOF_LONG_LONG 8
| #define SIZEOF_FLOAT 4
| #define SIZEOF_DOUBLE 8
| #define ALIGNOF_OBJC_OBJECT 8
| #define CON_AUTOLOAD 1
| #define HAVE_LIBDL 1
| #define HAVE_DLADDR 1
| #define HAVE_DECL_GETHOSTBYNAME_R 1
| #define HAVE_GETHOSTBYNAME_R 1
| #define HAVE_GETADDRINFO 1
| #define HAVE_RESOLV_H 1
| #define HAVE_PTHREAD_H 1
| #define SIZEOF_PTHREAD_MUTEX_T 40
| #define HAVE_PTHREAD_MUTEX_OWNER 1
| #define SIZEOF_PTHREAD_COND_T 48
| #define ALIGNOF_PTHREAD_MUTEX_T 8
| #define ALIGNOF_PTHREAD_COND_T 8
| #define HAVE_LIBRT 1
| #define PTHREAD_SETNAME(a) pthread_setname_np(pthread_self(),a)
| #define HAVE_PTHREAD_SPIN_LOCK 1
| #define HAVE_NANOSLEEP 1
| #define HAVE_USLEEP 1
| #define HAVE_OBJC_ROOT_CLASS_ATTRIBUTE 1
| #define HAVE_GETTID 1
| /* end confdefs.h.  */
| #include "./config/config.constant-string-class.m"
configure:9047: result: no
configure:9063: 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

[rfm]

Thanks.

The first line (the compiler invocation) includes '-fconstant-string-class=FooConstantString' telling clang to use FooConstantString as the constant string class.

We can see that clang then emits an error:

././config/config.constant-string-class.m:64:23: error: incompatible pointer types initializing 'FooConstantString *' with an expression of type 'NSString *' [-Wincompatible-pointer-types]
64 | FooConstantString *string = @"Antonio Valente";
| ^ ~~~~~~~~~~~~~~~~~~

So this is complaining that it can't assign a constant string value ( to a variable whose type is FooConstantString. So that's clearly a compiler bug: either it is creating a constant string of the wrong class (so the error message is correctly telling us the types are not compatible), or it's generating an error when it shouldn't.

I think that means you need to raise the issue of the bug with the clang/llvm developers so that they can fix the compiler.

That being said, what we actually need (for gnustep-base) is to be able to tell clang to use the class NSConstantString (which is what the base library provides), and the compiler may be doing that by default (ignoring the -fconstant-string-class setting) anyway, so as a workaround for the bug you could try changing the configure script to use NSConstantString rather than FooConstantString and see if that fixes it.

[mcarans]

@rfm I tried changing line 9013 in configure to:

  CPPFLAGS="$CPPFLAGS -fconstant-string-class=NSConstantString"

This still failed with:

configure:9014: checking if the compiler supports -fconstant-string-class
configure:9028: clang -o conftest -g -O2  -I/usr/local/include -I/usr/local/include -I/usr/local/include -I/usr/local/include  -x objective-c -fconstant-string-class=NSConstantString  -L/usr/local/lib -L/usr/local/lib -L/usr/local/lib -L/usr/local/lib conftest.c -lrt -ldl  -lresolv -lpthread -pthread -fexceptions -rdynamic -fobjc-runtime=gnustep-2.2 -fblocks -L/home/mcarans/GNUstep/Library/Libraries -L/usr/local/lib -lpthread -lobjc -lm   -lpthread  >&5
In file included from conftest.c:125:
In file included from ././config/config.constant-string-class.m:20:
././config/objc-common.g:54:3: warning: assignment to Objective-C's isa is deprecated in favor of object_setClass() [-Wdeprecated-objc-isa-usage]
   54 |   obj->isa = self;
      |   ^  ~~~~~~~     
      |   object_setClass( , )
././config/objc-common.g:47:5: note: instance variable is declared here
   47 |  id isa;
      |     ^
In file included from conftest.c:125:
././config/config.constant-string-class.m:56:12: warning: returning 'const char *const' from a function with result type 'char *' discards qualifiers [-Wincompatible-pointer-types-discards-qualifiers]
   56 |     return c_string;
      |            ^~~~~~~~
././config/config.constant-string-class.m:64:23: error: incompatible pointer types initializing 'FooConstantString *' with an expression of type 'NSString *' [-Wincompatible-pointer-types]
   64 |    FooConstantString *string = @"Antonio Valente";
      |                       ^        ~~~~~~~~~~~~~~~~~~
2 warnings and 1 error generated.
configure:9028: $? = 1
configure: program exited with status 1
configure: failed program was:
| /* confdefs.h */
| #define PACKAGE_NAME ""
| #define PACKAGE_TARNAME ""
| #define PACKAGE_VERSION ""
| #define PACKAGE_STRING ""
| #define PACKAGE_BUGREPORT ""
| #define PACKAGE_URL ""
| #define OPTION_NO_ENVIRONMENT 0
| #define GNUSTEP_TARGET_MAKEFILES "/usr/local/share/GNUstep/Makefiles"
| #define GNUSTEP_TARGET_USER_DEFAULTS_DIR "GNUstep/Defaults"
| #define GNUSTEP_TARGET_USER_CONFIG_FILE ".GNUstep.conf"
| #define GNUSTEP_TARGET_CONFIG_FILE "/usr/local/etc/GNUstep/GNUstep.conf"
| #define GNUSTEP_TARGET_SYSTEM_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_SYSTEM_ADMIN_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_SYSTEM_WEB_APPS "/usr/local/lib/GNUstep/WebApplications"
| #define GNUSTEP_TARGET_SYSTEM_TOOLS "/usr/local/bin"
| #define GNUSTEP_TARGET_SYSTEM_ADMIN_TOOLS "/usr/local/sbin"
| #define GNUSTEP_TARGET_SYSTEM_LIBRARY "/usr/local/lib/GNUstep"
| #define GNUSTEP_TARGET_SYSTEM_LIBRARIES "/usr/local/lib"
| #define GNUSTEP_TARGET_SYSTEM_SERVICES "/usr/local/lib/GNUstep/Services"
| #define GNUSTEP_TARGET_SYSTEM_HEADERS "/usr/local/include"
| #define GNUSTEP_TARGET_SYSTEM_DOC "/usr/local/share/GNUstep/Documentation"
| #define GNUSTEP_TARGET_SYSTEM_DOC_MAN "/usr/local/share/man"
| #define GNUSTEP_TARGET_SYSTEM_DOC_INFO "/usr/local/share/info"
| #define GNUSTEP_TARGET_NETWORK_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_NETWORK_ADMIN_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_NETWORK_WEB_APPS "/usr/local/lib/GNUstep/WebApplications"
| #define GNUSTEP_TARGET_NETWORK_TOOLS "/usr/local/bin"
| #define GNUSTEP_TARGET_NETWORK_ADMIN_TOOLS "/usr/local/sbin"
| #define GNUSTEP_TARGET_NETWORK_LIBRARY "/usr/local/lib/GNUstep"
| #define GNUSTEP_TARGET_NETWORK_LIBRARIES "/usr/local/lib"
| #define GNUSTEP_TARGET_NETWORK_SERVICES "/usr/local/lib/GNUstep/Services"
| #define GNUSTEP_TARGET_NETWORK_HEADERS "/usr/local/include"
| #define GNUSTEP_TARGET_NETWORK_DOC "/usr/local/share/GNUstep/Documentation"
| #define GNUSTEP_TARGET_NETWORK_DOC_MAN "/usr/local/share/man"
| #define GNUSTEP_TARGET_NETWORK_DOC_INFO "/usr/local/share/info"
| #define GNUSTEP_TARGET_LOCAL_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_LOCAL_ADMIN_APPS "/usr/local/lib/GNUstep/Applications"
| #define GNUSTEP_TARGET_LOCAL_WEB_APPS "/usr/local/lib/GNUstep/WebApplications"
| #define GNUSTEP_TARGET_LOCAL_TOOLS "/usr/local/bin"
| #define GNUSTEP_TARGET_LOCAL_ADMIN_TOOLS "/usr/local/sbin"
| #define GNUSTEP_TARGET_LOCAL_LIBRARY "/usr/local/lib/GNUstep"
| #define GNUSTEP_TARGET_LOCAL_LIBRARIES "/usr/local/lib"
| #define GNUSTEP_TARGET_LOCAL_SERVICES "/usr/local/lib/GNUstep/Services"
| #define GNUSTEP_TARGET_LOCAL_HEADERS "/usr/local/include"
| #define GNUSTEP_TARGET_LOCAL_DOC "/usr/local/share/GNUstep/Documentation"
| #define GNUSTEP_TARGET_LOCAL_DOC_MAN "/usr/local/share/man"
| #define GNUSTEP_TARGET_LOCAL_DOC_INFO "/usr/local/share/info"
| #define GNUSTEP_TARGET_USER_DIR_APPS "GNUstep/Applications"
| #define GNUSTEP_TARGET_USER_DIR_ADMIN_APPS "GNUstep/Applications/Admin"
| #define GNUSTEP_TARGET_USER_DIR_WEB_APPS "GNUstep/WebApplications"
| #define GNUSTEP_TARGET_USER_DIR_TOOLS "GNUstep/Tools"
| #define GNUSTEP_TARGET_USER_DIR_ADMIN_TOOLS "GNUstep/Tools/Admin"
| #define GNUSTEP_TARGET_USER_DIR_LIBRARY "GNUstep/Library"
| #define GNUSTEP_TARGET_USER_DIR_LIBRARIES "GNUstep/Library/Libraries"
| #define GNUSTEP_TARGET_USER_DIR_SERVICES "/Services"
| #define GNUSTEP_TARGET_USER_DIR_HEADERS "GNUstep/Library/Headers"
| #define GNUSTEP_TARGET_USER_DIR_DOC "GNUstep/Library/Documentation"
| #define GNUSTEP_TARGET_USER_DIR_DOC_MAN "GNUstep/Library/Documentation/man"
| #define GNUSTEP_TARGET_USER_DIR_DOC_INFO "GNUstep/Library/Documentation/info"
| #define GNUSTEP_TARGET_SYSTEM_USERS_DIR ""
| #define GNUSTEP_TARGET_NETWORK_USERS_DIR ""
| #define GNUSTEP_TARGET_LOCAL_USERS_DIR ""
| #define HAVE_STDIO_H 1
| #define HAVE_STDLIB_H 1
| #define HAVE_STRING_H 1
| #define HAVE_INTTYPES_H 1
| #define HAVE_STDINT_H 1
| #define HAVE_STRINGS_H 1
| #define HAVE_SYS_STAT_H 1
| #define HAVE_SYS_TYPES_H 1
| #define HAVE_UNISTD_H 1
| #define HAVE_WCHAR_H 1
| #define STDC_HEADERS 1
| #define _ALL_SOURCE 1
| #define _DARWIN_C_SOURCE 1
| #define _GNU_SOURCE 1
| #define _HPUX_ALT_XOPEN_SOCKET_API 1
| #define _NETBSD_SOURCE 1
| #define _OPENBSD_SOURCE 1
| #define _POSIX_PTHREAD_SEMANTICS 1
| #define __STDC_WANT_IEC_60559_ATTRIBS_EXT__ 1
| #define __STDC_WANT_IEC_60559_BFP_EXT__ 1
| #define __STDC_WANT_IEC_60559_DFP_EXT__ 1
| #define __STDC_WANT_IEC_60559_FUNCS_EXT__ 1
| #define __STDC_WANT_IEC_60559_TYPES_EXT__ 1
| #define __STDC_WANT_LIB_EXT2__ 1
| #define __STDC_WANT_MATH_SPEC_FUNCS__ 1
| #define _TANDEM_SOURCE 1
| #define __EXTENSIONS__ 1
| #define HAVE_FSEEKO 1
| #define USE_ATOMIC_BUILTINS 1
| #define HAVE_OBJC_RUNTIME_H 1
| #define HAVE_OBJC_OBJC_H 1
| #define HAVE_VISIBILITY_ATTRIBUTE 1
| #define SIZEOF_VOIDP 8
| #define SIZEOF_SHORT 2
| #define SIZEOF_INT 4
| #define SIZEOF_LONG 8
| #define SIZEOF_LONG_LONG 8
| #define SIZEOF_FLOAT 4
| #define SIZEOF_DOUBLE 8
| #define ALIGNOF_OBJC_OBJECT 8
| #define CON_AUTOLOAD 1
| #define HAVE_LIBDL 1
| #define HAVE_DLADDR 1
| #define HAVE_DECL_GETHOSTBYNAME_R 1
| #define HAVE_GETHOSTBYNAME_R 1
| #define HAVE_GETADDRINFO 1
| #define HAVE_RESOLV_H 1
| #define HAVE_PTHREAD_H 1
| #define SIZEOF_PTHREAD_MUTEX_T 40
| #define HAVE_PTHREAD_MUTEX_OWNER 1
| #define SIZEOF_PTHREAD_COND_T 48
| #define ALIGNOF_PTHREAD_MUTEX_T 8
| #define ALIGNOF_PTHREAD_COND_T 8
| #define HAVE_LIBRT 1
| #define PTHREAD_SETNAME(a) pthread_setname_np(pthread_self(),a)
| #define HAVE_PTHREAD_SPIN_LOCK 1
| #define HAVE_NANOSLEEP 1
| #define HAVE_USLEEP 1
| #define HAVE_OBJC_ROOT_CLASS_ATTRIBUTE 1
| #define HAVE_GETTID 1
| /* end confdefs.h.  */
| #include "./config/config.constant-string-class.m"
configure:9047: result: no
configure:9063: 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

Did I change the correct line in configure?

Also I found this 2016 llvm bug report which seems related: llvm/llvm-project#27505. What do you think? Is it a bug that was fixed but there's been a regression in clang 22?

AI suggested changing line 64 of config.constant-string-class.m to:

FooConstantString *string = (FooConstantString *)@"Antonio Valente";

AI explained its reasoning:
"The configure script fails to detect support for -fconstant-string-class when using Clang 22+. While the compiler still supports the flag, it now treats the assignment of a literal to a custom class pointer as a hard error (-Wincompatible-pointer-types) rather than a permissive assignment...

Starting with recent LLVM/Clang versions, the internal AST defaults to typing @"" literals as NSString *. Since FooConstantString is a root class in the test environment and not a subclass of NSString, the compiler rejects the initialization."

configure completed with this change. Does the change make sense?

[pkgdemon]

@rfm I am not sure if this helps or not but this workaround worked for me.

https://github.com/gershwin-desktop/gershwin-developer/blob/main/Library/Patches/configure-constant-string-class.patch

[rfm]

Did I change the correct line in configure?
Not enough; you would need to change both places: the command line argument and the class name in the test program (config/constant-string-class.m)

Also I found this 2016 llvm bug report which seems related: llvm/llvm-project#27505. What do you think? Is it a bug that was fixed but there's been a regression in clang 22?
Yes I agree that it sounds exactly like the same symptoms, so it could well be a regression to the same bug.

The point of the -fconstant-string-class= command line option is to tell the compiler what class to use for constant strings, so the compiler really ought to know that it is safe/correct to assign a constant string to a variable of that class.

The function of the autoconf test is to check that this is supported. Specifically it checks that the command-line argument is accepted (the compiler doesn't abort when it sees '-fconstant-string-class=FooConstantString') and that the compiler uses the supplied value when compiling the code (it generates code to assign a constant string to a variable of the FooConstantString class), and that the resulting code actually works (calling a method from the specified class on a constant string instance produces the expected result).
The compiler error is occurring at the second part of the test :-(

pkgdemon's workaround, if I read it right, is to disable the check entirely and trust that things will be OK (apparently they are) within the base library itself, because the base library declares/defines both NSString and NSConstantString.
That means that the compiler is correctly setting/using the constant string class (so it links to the correct code in the base library), but it just doesn't know that when it comes to checking types for assignments etc.

Si I guess a better workaround would be to try to use a cast to tell the compiler it's ok to assign the constant string. That loses the second part of the test but keeps the most important bit (the check that the generated test code actually works).

I have committed a change to do that.

[pkgdemon]

I can confirm your fix works for me @rfm thanks

[mcarans]

Works for me too, thanks!