This way, tracking segment-to-section mapping becomes a lot easier
since it's effectively just start index plus number of sections
defined within the segment. If a section becomes empty however
care needs to be taken to remove the header upon committing to the
final binary.
Fix incorrect writing of symtab and strtab in dSYM bundle in incremental
context.
Fix incorrectly navigating unnamed consts (freeing) in incremental context.
This is currently hard-coded to require all consts to land in `__TEXT,__const`,
which is wrong and needs a rewrite.
Instead of generating sections upfront, allow generation by scanning
the object files for input -> output sections mapping. Next, always
strive to keep output sections in the final container sorted as they
appear in the final binary. This makes the linker less messy wrt
handling of output sections sort order for dyld/macOS not to complain.
There's still more work to be done for incremental context though
to make this work but looks promising already.
Shared libraries can be provided on the command line as if they were
objects, as a path to the ".so" file. The "each-lib-rpath" functionality
was ignoring these shared libraries accidentally, causing missing rpaths
in the output executable.
Now instead of zig.h being baked into the compiler binary, it is a
header file distributed along with all the other header files
distributed with Zig.
Closes#11643
At least on Linux, the pwritev syscall checks the pointer and returns
EFAULT before it checks if the length is nonzero.
Perhaps this should be fixed in the standard library, however, these are
still improvements since they make the kernel do less work within the
syscall.
This reverts commit 7cbd586ace46a8e8cebab660ebca3cfc049305d9.
This is causing a fail to build from source:
```
./lib/std/fmt.zig:492:17: error: cannot format optional without a specifier (i.e. {?} or {any})
@compileError("cannot format optional without a specifier (i.e. {?} or {any})");
^
./src/link/MachO/Atom.zig:544:26: note: called from here
log.debug(" RELA({s}) @ {x} => %{d} in object({d})", .{
^
```
I looked at the code to fix it but none of those args are optionals.
Previously, we would get a pointer to a slot in the symbol table,
apply changes to the symbol, and return the pointer. This however
didn't take into account that the symbol table may be moved in memory
in-between the modification and return from the function (`fn placeDecl`).
Prior to my rewrite, this was not possible within the body of the said
function. However, my rewrite revamped how we allocate GOT atoms and
their matching symtab indexes, which now may cause a move in memory
of the container.
In x86_64 relocs, it can so happen that the compiler
refers to the same atom by both the actual assigned symbol
and the start of the section. In this case, we need to
link the two together so add an alias.
Now, each object file will store a mutable table of symbols that it
defines. Upon symbol resolution between object files, the symbol
will be updated with a globally allocated section ordinal and address
in virtual memory. If the object defines a globally available symbol,
its location only (comprising of the symbol index and object index)
will be stored in the globals map for easy access when relocating, etc.
This approach cleans up the symbol management significantly, and matches
the status quo used in zld/ELF.
Additionally, this makes scoping symbol stabs easier too as they are
now naturally contained within each object file.
* test/link: initial wasm support
This adds basic parsing and dumping of wasm section so they
can be tested using the new linker-test infrastructure.
* test/link: all wasm sections parsing and dumping
We now parse and dump all sections for the wasm binary format.
Currently, this only dumps the name of a custom section.
Later this should also dump symbol table, name, linking metadata and relocations.
All of those live within the custom sections.
* Add wasm linker test
This also fixes a parser mistake in reading the flags.
* test/link: implement linker tests wasm & fixes
Adds several test cases to test the wasm self-hosted linker.
This also introduces fixes that were caught during the implementation
of those tests.
* test-runner: obey omit_stage2 for standalone
When a standalone test requires stage2, but stage2 is omit
from the compiler, such test case will not be included as part
of the test suite that is being ran. This is to support CI's
where we omit stage2 to lower the memory usage.
* make the setting in the linker backend be non-optional; by this time
all defaults are supposed to be resolved.
* integrate with `zig cc`
* change the CLI parsing to match C compiler parsing, allowing
`--compress-debug-sections` alone to choose a default encoding of
zlib.
Future improvement: make plain error notes actually render as notes
rather than errors, but keep them as errors for the case of
sub-compilation errors, e.g. when compiler-rt has compilation errors.
This is a prelude to a more elaborate work which will implement
`-dead_strip` flag - garbage collection of unreachable atoms. Here,
when sorting sections, we also check that the section is actually
populated with some atoms, and if not, we exclude it from the final
linked image. This can happen when we do not import any symbols
from dynamic libraries in which case we will not be populating
the stubs sections or the GOT table, implying we can skip allocating
those sections. Furthermore, we also make a check that a segment
is actually occupied too, with the exception of `__TEXT` segment
which is non-optional given that it wraps the header and load commands
and thus is required by the `dyld` to perform dynamic linking, and
`__PAGEZERO` which is generally non-optional when the linked image
is an executable. For any other segment, if its section count is
zero, we mark it as dead and skip allocating it and generating
a load command for it.
This commit also includes some minor improvements to the linker such
as refactoring of the segment allocating codepaths, skipping
`__PAGEZERO` generation for dylibs, and skipping generation of zero-sized
atoms for special symbols such as `__mh_execute_header` and `___dso_handle`.
These special symbols are only allocated local and global symbol pair
and their VM addresses is set to the start of the `__TEXT` segment,
but no `Atom` is created, as it's not necessary given that they never
carry any machine code.
Finally, we now always force-link against `libSystem` which turns out
to be required for `dyld` to properly handle `LC_MAIN` load command
on older macOS versions such as 10.15.7.
