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Text file src/runtime/cgo/gcc_util.c

Documentation: runtime/cgo

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	#include "libcgo.h"
     6	
     7	/* Stub for creating a new thread */
     8	void
     9	x_cgo_thread_start(ThreadStart *arg)
    10	{
    11		ThreadStart *ts;
    12	
    13		/* Make our own copy that can persist after we return. */
    14		_cgo_tsan_acquire();
    15		ts = malloc(sizeof *ts);
    16		_cgo_tsan_release();
    17		if(ts == nil) {
    18			fprintf(stderr, "runtime/cgo: out of memory in thread_start\n");
    19			abort();
    20		}
    21		*ts = *arg;
    22	
    23		_cgo_sys_thread_start(ts);	/* OS-dependent half */
    24	}
    25	
    26	#ifndef CGO_TSAN
    27	void(* const _cgo_yield)() = NULL;
    28	#else
    29	
    30	#include <string.h>
    31	
    32	/*
    33	Stub for allowing libc interceptors to execute.
    34	
    35	_cgo_yield is set to NULL if we do not expect libc interceptors to exist.
    36	*/
    37	static void
    38	x_cgo_yield()
    39	{
    40		/*
    41		The libc function(s) we call here must form a no-op and include at least one
    42		call that triggers TSAN to process pending asynchronous signals.
    43	
    44		sleep(0) would be fine, but it's not portable C (so it would need more header
    45		guards).
    46		free(NULL) has a fast-path special case in TSAN, so it doesn't
    47		trigger signal delivery.
    48		free(malloc(0)) would work (triggering the interceptors in malloc), but
    49		it also runs a bunch of user-supplied malloc hooks.
    50	
    51		So we choose strncpy(_, _, 0): it requires an extra header,
    52		but it's standard and should be very efficient.
    53		*/
    54		char nothing = 0;
    55		strncpy(&nothing, &nothing, 0);
    56	}
    57	
    58	void(* const _cgo_yield)() = &x_cgo_yield;
    59	
    60	#endif  /* GO_TSAN */

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