crti.o/crtn.o is a legacy strategy for calling constructor functions
upon object loading that has been superseded by the
init_array/fini_array mechanism.
Zig code depends on neither, since the language intentionally has no way
to initialize data at runtime, but alas the Zig linker still must
support this feature since popular languages depend on it.
Anyway, the way it works is that crti.o has the machine code prelude of
two functions called _init and _fini, each in their own section with the
respective name. crtn.o has the machine code instructions comprising the
exitlude for each function. In between, objects use the .init and .fini
link section to populate the function body.
This function is then expected to be called upon object initialization
and deinitialization.
This mechanism is depended on by libc, for example musl and glibc, but
only for older ISAs. By the time the libcs gained support for newer
ISAs, they had moved on to the init_array/fini_array mechanism instead.
For the Zig linker, we are trying to move the linker towards
order-independent objects which is incompatible with the legacy
crti/crtn mechanism.
Therefore, this commit drops support entirely for crti/crtn mechanism,
which is necessary since the other commits in this branch make it
nondeterministic in which order the libc objects and the other link
inputs are sent to the linker.
The linker is still expected to produce a deterministic output, however,
by ignoring object input order for the purposes of symbol resolution.
This is necessary to inform the real, non-stub glibc that a program built with
Zig is using a modern `FILE` structure, i.e. glibc 2.1+. This is particularly
important on lesser-used architectures where the legacy code is poorly tested;
for example, glibc 2.40 introduced a regression for the legacy case in the
libio cleanup code, causing all Zig-compiled MIPS binaries to crash on exit.
glibc_runtime_check.c is a simple test case that exercises glibc functions
that might smoke out linking problems with Zig's C compiler. The
build.zig compiles it against a variety of glibc versions.
Also document and test glibc v2.2.5 (from 2002) as the oldest working
glibc target for C binaries.
The fstat,lstat,stat,mknod stubs used to build older (before v2.33)
glibc versions depend on the weak_hidden_alias macro. It was removed
from the glibc libc-symbols header, so patch it back in for the older
builds.
The scope of libc_nonshared.a was greatly changed in glibc 2.33 and
2.34, but only the change from 2.34 was reflected so far. Glibc 2.33
finally switched to versioned symbols for stat functions, meaning that
libc_nonshared.a no longer contains them since 2.33. Relevant files were
therefore reverted to 2.32 versions and renamed accordingly.
This commit also removes errno.c, which was probably added to
libc_nonshared.a based on a wrong assumption that glibc/include/errno.h
requires glibc/csu/errno.c. In reality errno.h should refer to
__libc_errno (not to be confused with the public __errno_location),
which should be imported from libc.so. The inclusion of errno.c resulted
in wrong compile options as well; this commit fixes them as well.
These are tripping on 32-bit x86 but are intended to prevent glibc
itself from being built with a bad configuration. Zig is only using this
file to create libc_nonshared.a, so it's not relevant.
This is the only place in all of glibc that this macro is referenced.
What is it doing? Only preventing fstatat.c from knowing the type
definition of `__time64_t`, apparently.
Fixes compilation of fstatat.c on 32-bit x86.
I could have just included the file from upstream glibc, but it was too
silly so I just inlined it. This patch could be dropped in a future
glibc update if desired. If omitted it will cause easily solvable
C compilation failures building glibc nonshared.
- `fcntl` was renamed to `fcntl64` in glibc 2.28 (see #9485)
- `res_{,n}{search,query,querydomain}` became "their own" symbols since
glibc 2.34: they were prefixed with `__` before.
This PR makes it possible to use `fcntl` with glibc 2.27 or older and
the `res_*` functions with glibc 2.33 or older.
These patches will become redundant with universal-headers and can be
dropped. But we have to do with what we have now.
The fstat,lstat,stat,mknod stubs used to build older (before v2.33)
glibc versions depend on the weak_hidden_alias macro. It was removed
from the glibc libc-symbols header, so patch it back in for the older
builds.
The scope of libc_nonshared.a was greatly changed in glibc 2.33 and
2.34, but only the change from 2.34 was reflected so far. Glibc 2.33
finally switched to versioned symbols for stat functions, meaning that
libc_nonshared.a no longer contains them since 2.33. Relevant files were
therefore reverted to 2.32 versions and renamed accordingly.
This commit also removes errno.c, which was probably added to
libc_nonshared.a based on a wrong assumption that glibc/include/errno.h
requires glibc/csu/errno.c. In reality errno.h should refer to
__libc_errno (not to be confused with the public __errno_location),
which should be imported from libc.so. The inclusion of errno.c resulted
in wrong compile options as well; this commit fixes them as well.
Fixes#16152
These are tripping on 32-bit x86 but are intended to prevent glibc
itself from being built with a bad configuration. Zig is only using this
file to create libc_nonshared.a, so it's not relevant.
This is the only place in all of glibc that this macro is referenced.
What is it doing? Only preventing fstatat.c from knowing the type
definition of `__time64_t`, apparently.
Fixes compilation of fstatat.c on 32-bit x86.
I could have just included the file from upstream glibc, but it was too
silly so I just inlined it. This patch could be dropped in a future
glibc update if desired. If omitted it will cause easily solvable
C compilation failures building glibc nonshared.
- `fcntl` was renamed to `fcntl64` in glibc 2.28 (see #9485)
- `res_{,n}{search,query,querydomain}` became "their own" symbols since
glibc 2.34: they were prefixed with `__` before.
This PR makes it possible to use `fcntl` with glibc 2.27 or older and
the `res_*` functions with glibc 2.33 or older.
These patches will become redundant with universal-headers and can be
dropped. But we have to do with what we have now.
Luna Schwalbe