From 47ab3d4a42e9ab51c465c4322d2ec233f6324e6b Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Sun, 28 Apr 2024 15:16:40 +0200 Subject: Adding upstream version 1.18.10. Signed-off-by: Daniel Baumann --- src/runtime/cgo/gcc_util.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 69 insertions(+) create mode 100644 src/runtime/cgo/gcc_util.c (limited to 'src/runtime/cgo/gcc_util.c') diff --git a/src/runtime/cgo/gcc_util.c b/src/runtime/cgo/gcc_util.c new file mode 100644 index 0000000..3fcb48c --- /dev/null +++ b/src/runtime/cgo/gcc_util.c @@ -0,0 +1,69 @@ +// Copyright 2009 The Go Authors. All rights reserved. +// Use of this source code is governed by a BSD-style +// license that can be found in the LICENSE file. + +#include "libcgo.h" + +/* Stub for creating a new thread */ +void +x_cgo_thread_start(ThreadStart *arg) +{ + ThreadStart *ts; + + /* Make our own copy that can persist after we return. */ + _cgo_tsan_acquire(); + ts = malloc(sizeof *ts); + _cgo_tsan_release(); + if(ts == nil) { + fprintf(stderr, "runtime/cgo: out of memory in thread_start\n"); + abort(); + } + *ts = *arg; + + _cgo_sys_thread_start(ts); /* OS-dependent half */ +} + +#ifndef CGO_TSAN +void(* const _cgo_yield)() = NULL; +#else + +#include + +char x_cgo_yield_strncpy_src = 0; +char x_cgo_yield_strncpy_dst = 0; +size_t x_cgo_yield_strncpy_n = 0; + +/* +Stub for allowing libc interceptors to execute. + +_cgo_yield is set to NULL if we do not expect libc interceptors to exist. +*/ +static void +x_cgo_yield() +{ + /* + The libc function(s) we call here must form a no-op and include at least one + call that triggers TSAN to process pending asynchronous signals. + + sleep(0) would be fine, but it's not portable C (so it would need more header + guards). + free(NULL) has a fast-path special case in TSAN, so it doesn't + trigger signal delivery. + free(malloc(0)) would work (triggering the interceptors in malloc), but + it also runs a bunch of user-supplied malloc hooks. + + So we choose strncpy(_, _, 0): it requires an extra header, + but it's standard and should be very efficient. + + GCC 7 has an unfortunate habit of optimizing out strncpy calls (see + https://golang.org/issue/21196), so the arguments here need to be global + variables with external linkage in order to ensure that the call traps all the + way down into libc. + */ + strncpy(&x_cgo_yield_strncpy_dst, &x_cgo_yield_strncpy_src, + x_cgo_yield_strncpy_n); +} + +void(* const _cgo_yield)() = &x_cgo_yield; + +#endif /* GO_TSAN */ -- cgit v1.2.3