multiple definitions of tet_thistest and others.

$ meson setup build
The Meson build system
Version: 1.0.1
Source dir: /home/uli/work/xts
Build dir: /home/uli/work/xts/build
Build type: native build
Project name: X Test Suite
Project version: 0.99.1
C compiler for the host machine: cc (gcc 12.2.0 "cc (Debian 12.2.0-14) 12.2.0")
C linker for the host machine: cc ld.bfd 2.40
Host machine cpu family: x86_64
Host machine cpu: x86_64
Compiler for C supports arguments -w: YES 
First supported argument: -w
Found pkg-config: /usr/bin/pkg-config (1.8.1)
Run-time dependency x11 found: YES 1.8.4
Run-time dependency xext found: YES 1.3.4
Run-time dependency xi found: YES 1.8
Run-time dependency xtst found: YES 1.2.3
Run-time dependency xau found: YES 1.0.9
Run-time dependency xtrans found: YES 1.4.0
Run-time dependency xmu found: YES 1.1.3
Run-time dependency xaw7 found: YES 1.0.14
Program bdftopcf found: YES (/usr/bin/bdftopcf)
Program mkfontdir found: YES (/usr/bin/mkfontdir)
Program sed found: YES (/usr/bin/sed)
Program perl found: YES (/usr/bin/perl)
Program xset found: YES (/usr/bin/xset)
Program xdpyinfo found: YES (/usr/bin/xdpyinfo)
Program python3 found: YES (/usr/bin/python3)
Program asciidoc found: YES (/usr/bin/asciidoc)
Program xmlto found: YES (/usr/bin/xmlto)
Configuring config.h using configuration
Program sh found: YES (/usr/bin/sh)
Build targets in project: 1124
NOTICE: Future-deprecated features used:
 * 0.56.0: {'meson.build_root', 'meson.source_root'}
 * 0.60.0: {'install_subdir with empty directory'}

Found ninja-1.11.1 at /usr/bin/ninja

Running 'ninja -C build' compiles a while, then it aborts with these errors:

...
[430/3695] Linking target xts5/Xproto/pAllocColorCells
FAILED: xts5/Xproto/pAllocColorCells 
cc  -o xts5/Xproto/pAllocColorCells xts5/Xproto/pAllocColorCells.p/meson-generated_pAllocColorCells.m.c.o -Wl,--as-needed -Wl,--no-undefined '-Wl,-rpath,$ORIGIN/../src:$ORIGIN/../../src/tet3/apilib' -Wl,-rpath-link,/home/uli/work/xts/build/xts5/src -Wl,-rpath-link,/home/uli/work/xts/build/src/tet3/apilib -Wl,--start-group xts5/src/libxts5proto.so xts5/src/libxts5.so src/tet3/apilib/libapi_s.so src/tet3/tcm/libtcmmain.a src/tet3/apilib/libapi.a src/tet3/tcm/libtcm.a /usr/lib/x86_64-linux-gnu/libX11.so /usr/lib/x86_64-linux-gnu/libXext.so /usr/lib/x86_64-linux-gnu/libXi.so /usr/lib/x86_64-linux-gnu/libXtst.so /usr/lib/x86_64-linux-gnu/libXau.so -Wl,--end-group
/usr/bin/ld: src/tet3/tcm/libtcmmain.a.p/tcm.c.o:/home/uli/work/xts/build/../src/tet3/tcm/tcm.c:96: multiple definition of `tet_thistest'; xts5/Xproto/pAllocColorCells.p/meson-generated_pAllocColorCells.m.c.o:/home/uli/work/xts/build/xts5/Xproto/pAllocColorCells.p/pAllocColorCells.m.c:183: first defined here
collect2: error: ld returned 1 exit status
[432/3695] Linking target xts5/Xproto/pAllocColor
FAILED: xts5/Xproto/pAllocColor 
cc  -o xts5/Xproto/pAllocColor xts5/Xproto/pAllocColor.p/meson-generated_pAllocColor.m.c.o -Wl,--as-needed -Wl,--no-undefined '-Wl,-rpath,$ORIGIN/../src:$ORIGIN/../../src/tet3/apilib' -Wl,-rpath-link,/home/uli/work/xts/build/xts5/src -Wl,-rpath-link,/home/uli/work/xts/build/src/tet3/apilib -Wl,--start-group xts5/src/libxts5proto.so xts5/src/libxts5.so src/tet3/apilib/libapi_s.so src/tet3/tcm/libtcmmain.a src/tet3/apilib/libapi.a src/tet3/tcm/libtcm.a /usr/lib/x86_64-linux-gnu/libX11.so /usr/lib/x86_64-linux-gnu/libXext.so /usr/lib/x86_64-linux-gnu/libXi.so /usr/lib/x86_64-linux-gnu/libXtst.so /usr/lib/x86_64-linux-gnu/libXau.so -Wl,--end-group
/usr/bin/ld: src/tet3/tcm/libtcmmain.a.p/tcm.c.o:/home/uli/work/xts/build/../src/tet3/tcm/tcm.c:96: multiple definition of `tet_thistest'; xts5/Xproto/pAllocColor.p/meson-generated_pAllocColor.m.c.o:/home/uli/work/xts/build/xts5/Xproto/pAllocColor.p/pAllocColor.m.c:169: first defined here
collect2: error: ld returned 1 exit status
[435/3695] Linking target xts5/Xproto/pAllocColorPlanes
FAILED: xts5/Xproto/pAllocColorPlanes 
cc  -o xts5/Xproto/pAllocColorPlanes xts5/Xproto/pAllocColorPlanes.p/meson-generated_pAllocColorPlanes.m.c.o -Wl,--as-needed -Wl,--no-undefined '-Wl,-rpath,$ORIGIN/../src:$ORIGIN/../../src/tet3/apilib' -Wl,-rpath-link,/home/uli/work/xts/build/xts5/src -Wl,-rpath-link,/home/uli/work/xts/build/src/tet3/apilib -Wl,--start-group xts5/src/libxts5proto.so xts5/src/libxts5.so src/tet3/apilib/libapi_s.so src/tet3/tcm/libtcmmain.a src/tet3/apilib/libapi.a src/tet3/tcm/libtcm.a /usr/lib/x86_64-linux-gnu/libX11.so /usr/lib/x86_64-linux-gnu/libXext.so /usr/lib/x86_64-linux-gnu/libXi.so /usr/lib/x86_64-linux-gnu/libXtst.so /usr/lib/x86_64-linux-gnu/libXau.so -Wl,--end-group
/usr/bin/ld: src/tet3/tcm/libtcmmain.a.p/tcm.c.o:/home/uli/work/xts/build/../src/tet3/tcm/tcm.c:96: multiple definition of `tet_thistest'; xts5/Xproto/pAllocColorPlanes.p/meson-generated_pAllocColorPlanes.m.c.o:/home/uli/work/xts/build/xts5/Xproto/pAllocColorPlanes.p/pAllocColorPlanes.m.c:183: first defined here
collect2: error: ld returned 1 exit status
[439/3695] Compiling C object xts5/Xopen/XKeysymToKeycode.p/XKeysymToKeycode_Test1.c.o
ninja: build stopped: subcommand failed.

I tried to fix these by adding "extern" to the "int tet_thistest" lines but the next iteration finds plenty of identical errors in more and more files. And even after fixing all of them I get more "multiple definitions" errors for keysyms_per_keycode and minkc and maxkc and ebuf and so on. And even after fixing them the final linking fails because it does not find ntests.

So this is currently unbuildable on Debian 12. I think there's something fundamentally wrong in the build process, maybe some special gcc flag is required?