host_bitness.c revision ee57375c96822790cc7f837b4fdf64a9c1d69b3a 
1// Copyright 2014 The Android Open Source Project
2//
3// This software is licensed under the terms of the GNU General Public
4// License version 2, as published by the Free Software Foundation, and
5// may be copied, distributed, and modified under those terms.
6//
7// This program is distributed in the hope that it will be useful,
8// but WITHOUT ANY WARRANTY; without even the implied warranty of
9// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
10// GNU General Public License for more details.
11
12#include "android/utils/host_bitness.h"
13
14#ifdef _WIN32
15#include <windows.h>
16#else
17#include <stdlib.h>
18#endif
19
20int android_getHostBitness(void) {
21#ifdef _WIN32
22    char directory[900];
23
24    // Retrieves the path of the WOW64 system directory, which doesn't
25    // exist on 32-bit systems.
26    unsigned len = GetSystemWow64Directory(directory, sizeof(directory));
27    if (len == 0) {
28        return 32;
29    } else {
30        return 64;
31    }
32#else // !_WIN32
33  /*
34     This function returns 64 if host is running 64-bit OS, or 32 otherwise.
35
36     It uses the same technique in ndk/build/core/ndk-common.sh.
37     Here are comments from there:
38
39  ## On Linux or Darwin, a 64-bit kernel (*) doesn't mean that the user-land
40  ## is always 32-bit, so use "file" to determine the bitness of the shell
41  ## that invoked us. The -L option is used to de-reference symlinks.
42  ##
43  ## Note that on Darwin, a single executable can contain both x86 and
44  ## x86_64 machine code, so just look for x86_64 (darwin) or x86-64 (Linux)
45  ## in the output.
46
47    (*) ie. The following code doesn't always work:
48        struct utsname u;
49        int host_runs_64bit_OS = (uname(&u) == 0 && strcmp(u.machine, "x86_64") == 0);
50  */
51    return system("file -L \"$SHELL\" | grep -q \"x86[_-]64\"") == 0 ? 64 : 32;
52#endif // !_WIN32
53}
54