add linker -wrap flag

[zachcheu]

Fixes: #15051

This passes -wrap through to the old.

Test

> cat wrap_example.c foo.c
#include <stdio.h>
extern int foo();
extern int __real_foo();

int __wrap_foo() {
    printf("wrap foo\n");
    return 0;
}

int __real_foo(){
    printf("real foo\n");
    return 0;
}

int main () {
    printf("foo:");foo();
    printf("wrapfoo:");__wrap_foo();
    printf("realfoo:");__real_foo();
    return 0;
}
#include <stdio.h>
int foo() {
    printf("foo\n");
    return 0;
}

> ./zig2 cc wrap_example.c foo.c  -Wl,-wrap,foo -o main

> ./main
foo:wrap foo
wrapfoo:wrap foo
realfoo:foo

[motiejus]

cc @kubkon

This is causing annoyance in Uber's Go Monorepo. If you agree this is a simple-enough change, can we get it landed?

[motiejus]

Also @zachcheu you may want to add Fixes: #15051 to the PR description, this will close #15051 automatically.

[kubkon]

Please bump the Compilation.link_hash_implementation_version in

zig/src/Compilation.zig

Lines 2185 to 2189 in 28d6dd7

	/// This is only observed at compile-time and used to emit a compile error
	/// to remind the programmer to update multiple related pieces of code that
	/// are in different locations. Bump this number when adding or deleting
	/// anything from the link cache manifest.
	pub const link_hash_implementation_version = 7;

and the wrap list is correctly put in cache in all relevant places.

Secondly, I see you've added -wrap flag which affects zig build-exe etc, however I don't see a matching addition to zig cc which would fall under `-Wl,"--wrap=symbol"' most likely. See

zig/src/main.zig

Line 1659 in 28d6dd7

.wl => {

[kubkon]

I don't see any reason in having --wrap here too.

[zachcheu]

Secondly, I see you've added -wrap flag which affects zig build-exe etc, however I don't see a matching addition to zig cc which would fall under `-Wl,"--wrap=symbol"' most likely.

I don't believe an explicit case -wrap case is necessary. The final else case takes care of flags that are split by comma

zig/src/main.zig

Line 1718 in 6f15eed

try linker_args.append(linker_arg);

-Wl,--wrap=symbol is taken care by

zig/src/main.zig

Line 1668 in 6f15eed

if (mem.indexOfScalar(u8, linker_arg, '=')) |equals_pos| {

Building from source captures both of these scenarios

> ./zig2 cc wrap_example.c foo.c  -Wl,-wrap,foo -o main

> ./main
foo:wrap foo
wrapfoo:wrap foo
realfoo:foo

> ./zig2 cc wrap_example.c foo.c  -Wl,-wrap=foo -o main

> ./main
foo:wrap foo
wrapfoo:wrap foo
realfoo:foo

I don't believe this flag is available for build-exe

> ./zig2 build-exe wrap_example.c foo.c  -Wl,-wrap=foo -o main
error: unrecognized parameter: '-Wl,-wrap=foo'

> ./zig2 build-exe wrap_example.c foo.c  -Wl,-wrap,foo -o main
error: unrecognized parameter: '-Wl,-wrap,foo'

[kubkon]

Good catch about -Wl,-wrap being implicitly handled in the loop - I missed that.

Re the latter, zig build-exe does not understand -Wl flag and should handle an explicit -wrap flag.

[zachcheu]

Is this what you mean by supporting zig build-exe?

> ./zig2 build-exe -lc main.c foo.c -wrap foo

> ./main
foo:wrap foo
wrapfoo:wrap foo
realfoo:foo

[andrewrk]

hi @zachcheu, I'm sorry for confusing you - I added a commit to the branch and force pushed, and then set to auto-merge once the CI tests passed. It looks like you attempted to push some other work after that just now, but ran into git troubles.

I can take it from here. Are you OK with that?

[zachcheu]

No worries. Feel free to take it from here. Thanks!