systemd fails to build w/ meson master

[thesamesam]

$ ~/git/meson/meson.py --version
1.10.99
$ ninja --version
1.13.2

$ git clone https://github.com/systemd/systemd && cd systemd
$ ~/git/meson/meson.py setup build -Dpassswdqc=disabled
$ ninja -C build
ninja: Entering directory `build'
ninja: Jobserver mode detected: -j32 -l32 --jobserver-auth=fifo:/dev/steve
[33/2675] Compiling C object src/libc/libc-wrapper.a.p/keyctl.c.o
FAILED: [code=1] src/libc/libc-wrapper.a.p/keyctl.c.o
/usr/bin/ccache cc -Isrc/libc/libc-wrapper.a.p -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=gnu17 -O0 -g -Wno-missing-field-initializers -Wno-unused-parameter -Wno-nonnull-compare -Warray-bounds -Warray-bounds=2 -Wdate-time -Wendif-labels -Werror=bool-compare -Werror=discarded-qualifiers -Werror=flex-array-member-not-at-end -Werror=format=2 -Werror=format-signedness -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=missing-declarations -Werror=missing-parameter-name -Werror=missing-prototypes -Werror=overflow -Werror=override-init -Werror=pointer-sign -Werror=return-type -Werror=sequence-point -Werror=shift-count-overflow -Werror=shift-overflow=2 -Werror=strict-flex-arrays -Werror=undef -Wfloat-equal -Wimplicit-fallthrough=5 -Winit-self -Wlogical-op -Wmissing-include-dirs -Wmissing-noreturn -Wnested-externs -Wold-style-definition -Wpointer-arith -Wredundant-decls -Wshadow -Wstrict-aliasing=2 -Wstrict-prototypes -Wsuggest-attribute=noreturn -Wunterminated-string-initialization -Wunused-function -Wwrite-strings -Wzero-as-null-pointer-constant -Wzero-length-bounds -fdiagnostics-show-option -fno-common -fstack-protector -fstack-protector-strong -fstrict-flex-arrays=3 --param=ssp-buffer-size=4 -Wno-unused-result -Werror=shadow -fPIC -fno-strict-aliasing -fstrict-flex-arrays=1 -fvisibility=hidden -fno-omit-frame-pointer -include config.h -isystem../src/include/uapi -isystemsrc/include/override -isystem../src/include/override -fvisibility=default -MD -MQ src/libc/libc-wrapper.a.p/keyctl.c.o -MF src/libc/libc-wrapper.a.p/keyctl.c.o.d -o src/libc/libc-wrapper.a.p/keyctl.c.o -c ../src/libc/keyctl.c
In file included from ../src/libc/keyctl.c:3:
../src/include/override/sys/keyctl.h:13:1: error: unknown type name ‘key_serial_t’
   13 | key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid);
      | ^~~~~~~~~~~~
../src/include/override/sys/keyctl.h:13:107: error: unknown type name ‘key_serial_t’
   13 | key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid);
      |                                                                                                           ^~~~~~~~~~~~
../src/include/override/sys/keyctl.h:18:1: error: unknown type name ‘key_serial_t’
   18 | key_serial_t missing_request_key(const char *type, const char *description, const char *callout_info, key_serial_t destringid);
      | ^~~~~~~~~~~~
../src/include/override/sys/keyctl.h:18:103: error: unknown type name ‘key_serial_t’
   18 | key_serial_t missing_request_key(const char *type, const char *description, const char *callout_info, key_serial_t destringid);
      |                                                                                                       ^~~~~~~~~~~~
../src/libc/keyctl.c:14:1: error: unknown type name ‘key_serial_t’
   14 | key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) {
      | ^~~~~~~~~~~~
../src/libc/keyctl.c:14:107: error: unknown type name ‘key_serial_t’
   14 | key_serial_t missing_add_key(const char *type, const char *description, const void *payload, size_t plen, key_serial_t ringid) {
      |                                                                                                           ^~~~~~~~~~~~
../src/libc/keyctl.c:20:1: error: unknown type name ‘key_serial_t’
   20 | key_serial_t missing_request_key(const char *type, const char *description, const char *callout_info, key_serial_t destringid) {
      | ^~~~~~~~~~~~
../src/libc/keyctl.c:20:103: error: unknown type name ‘key_serial_t’
   20 | key_serial_t missing_request_key(const char *type, const char *description, const char *callout_info, key_serial_t destringid) {
      |                                                                                                       ^~~~~~~~~~~~
[39/2675] Generating src/core/bpf/restrict-fs/restrict-fs.bpf.unstripped.o with a custom command
ninja: build stopped: subcommand failed.

[thesamesam]

Started with a6ddf25:

commit a6ddf25634927e9ffc7af43edd897741815dcd4a
Author:     Dylan Baker <dylan@pnwbakers.com>
AuthorDate: Tue Oct 28 14:12:03 2025 -0700
Commit:     Dylan Baker <dylan@pnwbakers.com>
CommitDate: Thu Jan 8 08:44:53 2026 -0800

    backend/ninja: Extend InlcudeDirs.rel_string_list for backend use

    This adds the ability to remove build directories that don't exist.

    This doesn't require a second call to reverse() because that was being
    used to switch the order of the build and src directories, but
    `rel_string_list` returns them in the expected order already.

 mesonbuild/backend/ninjabackend.py | 38 ++++++++++----------------------------
 mesonbuild/build.py                |  8 ++++++--
 2 files changed, 16 insertions(+), 30 deletions(-)

cc @dcbaker

[thesamesam]

$ cat /tmp/before
/usr/bin/ccache cc -Isrc/libc/libc-wrapper.a.p -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=gnu17 -O0 -g -Wno-missing-field-initializers -Wno-unused-parameter -Wno-nonnull-compare -Warray-bounds -Warray-bounds=2 -Wdate-time -Wendif-labels -Werror=bool-compare -Werror=discarded-qualifiers -Werror=flex-array-member-not-at-end -Werror=format=2 -Werror=format-signedness -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=missing-declarations -Werror=missing-parameter-name -Werror=missing-prototypes -Werror=overflow -Werror=override-init -Werror=pointer-sign -Werror=return-type -Werror=sequence-point -Werror=shift-count-overflow -Werror=shift-overflow=2 -Werror=strict-flex-arrays -Werror=undef -Wfloat-equal -Wimplicit-fallthrough=5 -Winit-self -Wlogical-op -Wmissing-include-dirs -Wmissing-noreturn -Wnested-externs -Wold-style-definition -Wpointer-arith -Wredundant-decls -Wshadow -Wstrict-aliasing=2 -Wstrict-prototypes -Wsuggest-attribute=noreturn -Wunterminated-string-initialization -Wunused-function -Wwrite-strings -Wzero-as-null-pointer-constant -Wzero-length-bounds -fdiagnostics-show-option -fno-common -fstack-protector -fstack-protector-strong -fstrict-flex-arrays=3 --param=ssp-buffer-size=4 -Wno-unused-result -Werror=shadow -fPIC -fno-strict-aliasing -fstrict-flex-arrays=1 -fvisibility=hidden -fno-omit-frame-pointer -include config.h -isystem../src/include/override -isystemsrc/include/override -isystem../src/include/uapi -fvisibility=default -MD -MQ src/libc/libc-wrapper.a.p/keyctl.c.o -MF src/libc/libc-wrapper.a.p/keyctl.c.o.d -o src/libc/libc-wrapper.a.p/keyctl.c.o -c ../src/libc/keyctl.c
$ cat /tmp/after
/usr/bin/ccache cc -Isrc/libc/libc-wrapper.a.p -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=gnu17 -O0 -g -Wno-missing-field-initializers -Wno-unused-parameter -Wno-nonnull-compare -Warray-bounds -Warray-bounds=2 -Wdate-time -Wendif-labels -Werror=bool-compare -Werror=discarded-qualifiers -Werror=flex-array-member-not-at-end -Werror=format=2 -Werror=format-signedness -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=missing-declarations -Werror=missing-parameter-name -Werror=missing-prototypes -Werror=overflow -Werror=override-init -Werror=pointer-sign -Werror=return-type -Werror=sequence-point -Werror=shift-count-overflow -Werror=shift-overflow=2 -Werror=strict-flex-arrays -Werror=undef -Wfloat-equal -Wimplicit-fallthrough=5 -Winit-self -Wlogical-op -Wmissing-include-dirs -Wmissing-noreturn -Wnested-externs -Wold-style-definition -Wpointer-arith -Wredundant-decls -Wshadow -Wstrict-aliasing=2 -Wstrict-prototypes -Wsuggest-attribute=noreturn -Wunterminated-string-initialization -Wunused-function -Wwrite-strings -Wzero-as-null-pointer-constant -Wzero-length-bounds -fdiagnostics-show-option -fno-common -fstack-protector -fstack-protector-strong -fstrict-flex-arrays=3 --param=ssp-buffer-size=4 -Wno-unused-result -Werror=shadow -fPIC -fno-strict-aliasing -fstrict-flex-arrays=1 -fvisibility=hidden -fno-omit-frame-pointer -include config.h -isystem../src/include/uapi -isystemsrc/include/override -isystem../src/include/override -fvisibility=default -MD -MQ src/libc/libc-wrapper.a.p/keyctl.c.o -MF src/libc/libc-wrapper.a.p/keyctl.c.o.d -o src/libc/libc-wrapper.a.p/keyctl.c.o -c ../src/libc/keyctl.c
$ git diff --no-index --word-diff /tmp/before /tmp/after
--- a/tmp/before
+++ b/tmp/after
@@ -1 +1 @@
/usr/bin/ccache cc -Isrc/libc/libc-wrapper.a.p -fdiagnostics-color=always -D_FILE_OFFSET_BITS=64 -Wall -Winvalid-pch -Wextra -std=gnu17 -O0 -g -Wno-missing-field-initializers -Wno-unused-parameter -Wno-nonnull-compare -Warray-bounds -Warray-bounds=2 -Wdate-time -Wendif-labels -Werror=bool-compare -Werror=discarded-qualifiers -Werror=flex-array-member-not-at-end -Werror=format=2 -Werror=format-signedness -Werror=implicit-function-declaration -Werror=implicit-int -Werror=incompatible-pointer-types -Werror=int-conversion -Werror=missing-declarations -Werror=missing-parameter-name -Werror=missing-prototypes -Werror=overflow -Werror=override-init -Werror=pointer-sign -Werror=return-type -Werror=sequence-point -Werror=shift-count-overflow -Werror=shift-overflow=2 -Werror=strict-flex-arrays -Werror=undef -Wfloat-equal -Wimplicit-fallthrough=5 -Winit-self -Wlogical-op -Wmissing-include-dirs -Wmissing-noreturn -Wnested-externs -Wold-style-definition -Wpointer-arith -Wredundant-decls -Wshadow -Wstrict-aliasing=2 -Wstrict-prototypes -Wsuggest-attribute=noreturn -Wunterminated-string-initialization -Wunused-function -Wwrite-strings -Wzero-as-null-pointer-constant -Wzero-length-bounds -fdiagnostics-show-option -fno-common -fstack-protector -fstack-protector-strong -fstrict-flex-arrays=3 --param=ssp-buffer-size=4 -Wno-unused-result -Werror=shadow -fPIC -fno-strict-aliasing -fstrict-flex-arrays=1 -fvisibility=hidden -fno-omit-frame-pointer -include config.h[--isystem../src/include/override -isystemsrc/include/override-] -isystem../src/include/uapi {+-isystemsrc/include/override -isystem../src/include/override+} -fvisibility=default -MD -MQ src/libc/libc-wrapper.a.p/keyctl.c.o -MF src/libc/libc-wrapper.a.p/keyctl.c.o.d -o src/libc/libc-wrapper.a.p/keyctl.c.o -c ../src/libc/keyctl.c

i.e.

-include config.h[--isystem../src/include/override -isystemsrc/include/override-] -isystem../src/include/uapi {+-isystemsrc/include/override -isystem../src/include/override+}

[dcbaker]

I am absolutely baffled by this regression. Our unit test gets exactly what it needs to compile correctly with no changes to the output at all from my patch, systemd ends up with everything reversed. If I switch to make systemd happy, our unit test gets everything reversed, and I am absolutely baffled on how that could happen

[dcbaker]

https://github.com/dcbaker/meson/pull/new/wip/2026-01/fix-systemd-regression

I'm just baffled. This fixes the issue you're pointing out, but causes other things to be completely reversed, even though there's only one caller, and I can't figure out how we could end up with it flipped in one situation, but right in the other.

[thierryreding]

Not sure if it helps, but I've run into this as well. However, I occasionally see this succeed and it looks like when it breaks it does so because of some extra packages that are installed.

For a bit more background: I have a set of scripts cobbled together that build a minimal root filesystem for testing and on the first run systemd seems to build just fine. However, if I try to rebuild systemd after the entire filesystem has been built, then it fails. I haven't found a good way yet to determine what other package might be influencing this. It could be keyutils since it's somewhat related, but I'm not sure.

I can run a few more tests to see if I can get any more information if you think it'd be helpful.

[thierryreding]

Oh my... that's embarrassing. Total wild goose chase. It was occasionally working because it wouldn't use the meson built from source and fall back to the host version instead. Sorry for the noise.

[dcbaker]

I wonder if there's another call to string_list somewhere else that's causing the issue here...

I'll have to look more at this, although I should probably build a simpler test case.

[bonzini]

Minimal testcase: test.tar.gz, see also #15577.

[bonzini]

I think the bug is that the prepend_prefixes does not include isystem?

[bonzini]

Ok, so #15577 fixes the systemd case, but it breaks

system_includes = [
        include_directories('uapi', is_system : true),
        include_directories('override', is_system : true),
]

because pre-1.11.0 Meson incorrectly changes it to -isystem../override -isystem../uapi. (#15577 is a draft because I was hoping that the above would work both pre and post that PR).

The only solution for both is to undo part of a6ddf25, which sucks bigly but is what is implemented in #15578.