gcc_libinit_windows.c

     1  // Copyright 2015 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  # ifdef __CYGWIN__
     6  #error "don't use the cygwin compiler to build native Windows programs; use MinGW instead"
     7  #else
     8  // Exclude the following code from Cygwin builds.
     9  // Cygwin doesn't implement process.h nor does it support _beginthread.
    10  
    11  #define WIN32_LEAN_AND_MEAN
    12  #include <windows.h>
    13  #include <process.h>
    14  
    15  #include <stdio.h>
    16  #include <stdlib.h>
    17  #include <errno.h>
    18  
    19  #include "libcgo.h"
    20  #include "libcgo_windows.h"
    21  
    22  // Ensure there's one symbol marked __declspec(dllexport).
    23  // If there are no exported symbols, the unfortunate behavior of
    24  // the binutils linker is to also strip the relocations table,
    25  // resulting in non-PIE binary. The other option is the
    26  // --export-all-symbols flag, but we don't need to export all symbols
    27  // and this may overflow the export table (#40795).
    28  // See https://sourceware.org/bugzilla/show_bug.cgi?id=19011
    29  __declspec(dllexport) int _cgo_dummy_export;
    30  
    31  static volatile LONG runtime_init_once_gate = 0;
    32  static volatile LONG runtime_init_once_done = 0;
    33  
    34  static CRITICAL_SECTION runtime_init_cs;
    35  
    36  static HANDLE runtime_init_wait;
    37  static int runtime_init_done;
    38  
    39  uintptr_t x_cgo_pthread_key_created;
    40  void (*x_crosscall2_ptr)(void (*fn)(void *), void *, int, size_t);
    41  
    42  // Pre-initialize the runtime synchronization objects
    43  void
    44  _cgo_preinit_init() {
    45  	 runtime_init_wait = CreateEvent(NULL, TRUE, FALSE, NULL);
    46  	 if (runtime_init_wait == NULL) {
    47  		fprintf(stderr, "runtime: failed to create runtime initialization wait event.\n");
    48  		abort();
    49  	 }
    50  
    51  	 InitializeCriticalSection(&runtime_init_cs);
    52  }
    53  
    54  // Make sure that the preinit sequence has run.
    55  void
    56  _cgo_maybe_run_preinit() {
    57  	 if (!InterlockedExchangeAdd(&runtime_init_once_done, 0)) {
    58  			if (InterlockedIncrement(&runtime_init_once_gate) == 1) {
    59  				 _cgo_preinit_init();
    60  				 InterlockedIncrement(&runtime_init_once_done);
    61  			} else {
    62  				 // Decrement to avoid overflow.
    63  				 InterlockedDecrement(&runtime_init_once_gate);
    64  				 while(!InterlockedExchangeAdd(&runtime_init_once_done, 0)) {
    65  						Sleep(0);
    66  				 }
    67  			}
    68  	 }
    69  }
    70  
    71  void
    72  x_cgo_sys_thread_create(void (*func)(void*), void* arg) {
    73  	_cgo_beginthread(func, arg);
    74  }
    75  
    76  int
    77  _cgo_is_runtime_initialized() {
    78  	 EnterCriticalSection(&runtime_init_cs);
    79  	 int status = runtime_init_done;
    80  	 LeaveCriticalSection(&runtime_init_cs);
    81  	 return status;
    82  }
    83  
    84  uintptr_t
    85  _cgo_wait_runtime_init_done(void) {
    86  	void (*pfn)(struct context_arg*);
    87  
    88  	 _cgo_maybe_run_preinit();
    89  	while (!_cgo_is_runtime_initialized()) {
    90  			WaitForSingleObject(runtime_init_wait, INFINITE);
    91  	}
    92  	pfn = _cgo_get_context_function();
    93  	if (pfn != nil) {
    94  		struct context_arg arg;
    95  
    96  		arg.Context = 0;
    97  		(*pfn)(&arg);
    98  		return arg.Context;
    99  	}
   100  	return 0;
   101  }
   102  
   103  // Should not be used since x_cgo_pthread_key_created will always be zero.
   104  void x_cgo_bindm(void* dummy) {
   105  	fprintf(stderr, "unexpected cgo_bindm on Windows\n");
   106  	abort();
   107  }
   108  
   109  void
   110  x_cgo_notify_runtime_init_done(void* dummy) {
   111  	 _cgo_maybe_run_preinit();
   112  
   113  	 EnterCriticalSection(&runtime_init_cs);
   114  	runtime_init_done = 1;
   115  	 LeaveCriticalSection(&runtime_init_cs);
   116  
   117  	 if (!SetEvent(runtime_init_wait)) {
   118  		fprintf(stderr, "runtime: failed to signal runtime initialization complete.\n");
   119  		abort();
   120  	}
   121  }
   122  
   123  // The context function, used when tracing back C calls into Go.
   124  static void (*cgo_context_function)(struct context_arg*);
   125  
   126  // Sets the context function to call to record the traceback context
   127  // when calling a Go function from C code. Called from runtime.SetCgoTraceback.
   128  void x_cgo_set_context_function(void (*context)(struct context_arg*)) {
   129  	EnterCriticalSection(&runtime_init_cs);
   130  	cgo_context_function = context;
   131  	LeaveCriticalSection(&runtime_init_cs);
   132  }
   133  
   134  // Gets the context function.
   135  void (*(_cgo_get_context_function(void)))(struct context_arg*) {
   136  	void (*ret)(struct context_arg*);
   137  
   138  	EnterCriticalSection(&runtime_init_cs);
   139  	ret = cgo_context_function;
   140  	LeaveCriticalSection(&runtime_init_cs);
   141  	return ret;
   142  }
   143  
   144  void _cgo_beginthread(void (*func)(void*), void* arg) {
   145  	int tries;
   146  	uintptr_t thandle;
   147  
   148  	for (tries = 0; tries < 20; tries++) {
   149  		thandle = _beginthread(func, 0, arg);
   150  		if (thandle == -1 && errno == EACCES) {
   151  			// "Insufficient resources", try again in a bit.
   152  			//
   153  			// Note that the first Sleep(0) is a yield.
   154  			Sleep(tries); // milliseconds
   155  			continue;
   156  		} else if (thandle == -1) {
   157  			break;
   158  		}
   159  		return; // Success!
   160  	}
   161  
   162  	fprintf(stderr, "runtime: failed to create new OS thread (%d)\n", errno);
   163  	abort();
   164  }
   165  
   166  #endif // __CYGWIN__
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