Bug 53265

Created attachment 65308 [details] [review]
fix incorrect autotools usage

The new hackery to extract syscalls from syscall.h just calls plain cpp and doesn't use CFLAGS even though CPP expands to "gcc -E" on all post-2000 linux platforms. This causes multi-arch (CFLAGS=-m32) and cross-compile builds of systemd to fail because the same syscalls aren't available everywhere.

Example with CFLAGS=-m32
[...]
  GEN    src/core/load-fragment-gperf.c
  GEN    src/core/load-fragment-gperf-nulstr.c
  CC     src/udev/libudev_core_la-udev-event.lo
  CC     src/udev/libudev_core_la-udev-watch.lo
  CC     src/udev/libudev_core_la-udev-node.lo
  CC     src/udev/libudev_core_la-udev-rules.lo
In file included from src/core/syscall-list.c:31:0:
src/core/syscall-to-name.h:6:2: error: ‘__NR_connect’ undeclared here (not in a function)
src/core/syscall-to-name.h:6:1: error: array index in initializer not of integer type
src/core/syscall-to-name.h:6:1: error: (near initialization for ‘syscall_names’)
src/core/syscall-to-name.h:21:2: error: ‘__NR_semop’ undeclared here (not in a function)
src/core/syscall-to-name.h:21:1: error: array index in initializer not of integer type
src/core/syscall-to-name.h:21:1: error: (near initialization for ‘syscall_names’)
src/core/syscall-to-name.h:23:2: error: ‘__NR_epoll_ctl_old’ undeclared here (not in a function)
src/core/syscall-to-name.h:23:1: error: array index in initializer not of integer type
src/core/syscall-to-name.h:23:1: error: (near initialization for ‘syscall_names’)
src/core/syscall-to-name.h:25:2: error: ‘__NR_shmat’ undeclared here (not in a function)
src/core/syscall-to-name.h:25:1: error: array index in initializer not of integer type
src/core/syscall-to-name.h:25:1: error: (near initialization for ‘syscall_names’)
src/core/syscall-to-name.h:30:2: error: ‘__NR_shmdt’ undeclared here (not in a function)
src/core/syscall-to-name.h:30:1: error: array index in initializer not of integer type
src/core/syscall-to-name.h:30:1: error: (near initialization for ‘syscall_names’)
src/core/syscall-to-name.h:52:2: error: ‘__NR_semctl’ undeclared here (not in a function)
src/core/syscall-to-name.h:52:1: error: array index in initializer not of integer type
src/core/syscall-to-name.h:52:1: error: (near initialization for ‘syscall_names’)
[...]

The attached patch fixes up all calls to CPP.

It assumes that CPP expands to "gcc -E" or something that accepts CFLAGS as parameters, but that's the case already with DBUS_PREPROCESS. It could be worked around in configure.ac if ever (god forbid) there was a linux system where CPP expands to plain cpp, but that's probably an academic exercise given the target group of systemd.

It looks to me like the problem was introduced because the person who introduced this feature saw that "cpp $BLA $FOO < /dev/null > foo.txt" worked and "$(CPP) $BLA $FOO < /dev/null > foo.txt" didn't. That's because gcc needs a dash before  < /dev/null to accept input on stdin.