编译Android源码时，gcc将中定义了__x86_64__，编译不过，错误如下。我的PC是32位的，应该如何设置？
这两天心血来潮，执行完 repo sync 后，顺手来了一下 make，不料却发现了以下的错误：
host C: libclearsilver-jni <= external/clearsilver/java-jni/j_neo_util.c In file included from /usr/include/features.h:378, from /usr/include/string.h:26, from external/clearsilver/java-jni/j_neo_util.c:1: /usr/include/gnu/stubs.h:9:27: error: gnu/stubs-64.h: No such file or directory make: *** [out/host/linux-x86/obj/SHARED_LIBRARIES/libclearsilver-jni_intermediates/j_neo_util.o] Error 1
兵来将挡，水来土掩，用关键字 android “error: gnu/stubs-64.h: no such file or directory” 来搜一下吧，发现搜索结果寥寥无几，看样子问题比较新，其中有一个链接，就顺手点了过去。帖子反映的问题和我一模一样，不过它的分析给了我一些提醒。
从错误信息入手，追踪到/usr/include/gnu/stubs.h，看到如下代码：
<SPAN style="COLOR: #339933">#if __WORDSIZE == 32</SPAN> <SPAN style="COLOR: #339933"># include <gnu/stubs-32.h></SPAN> <SPAN style="COLOR: #339933">#elif __WORDSIZE == 64</SPAN> <SPAN style="COLOR: #339933"># include <gnu/stubs-64.h></SPAN> <SPAN style="COLOR: #339933">#else</SPAN> <SPAN style="COLOR: #339933"># error "unexpected value for __WORDSIZE macro"</SPAN> <SPAN style="COLOR: #339933">#endif</SPAN>
#if __WORDSIZE == 32 # include <gnu/stubs-32.h> #elif __WORDSIZE == 64 # include <gnu/stubs-64.h> #else # error "unexpected value for __WORDSIZE macro" #endif顺着 WORDSIZE，进入/usr/include/bits/wordsize，发现：
<SPAN style="COLOR: #339933">#if defined __x86_64__</SPAN> <SPAN style="COLOR: #339933"># define __WORDSIZE 64</SPAN> <SPAN style="COLOR: #339933"># define __WORDSIZE_COMPAT32 1</SPAN> <SPAN style="COLOR: #339933">#else</SPAN> <SPAN style="COLOR: #339933"># define __WORDSIZE 32</SPAN> <SPAN style="COLOR: #339933">#endif</SPAN>
#if defined __x86_64__ # define __WORDSIZE 64 # define __WORDSIZE_COMPAT32 1 #else # define __WORDSIZE 32 #endif结合报错的信息，可以知道这里一定是有定义__x86_64__，执行一下 uname -a 可以确认 OS 明明是x86，为什么会__x86_64__呢？追根溯源， Android 源码或许能露出蛛丝马迹。
果不其然，从 android.git.kernel.org 的 platform/external/clearsilver.git 上，看到5天前，有个 Ying Wang 的家伙提交一个修改：Fix 64-bit clearsilver shared library issue，参看这里，修改内容中 java-jni/Android.mk，和出现本次问题的路径 java-jni/j_neo_util.c，同属一个父目录，看样子有点关系，查看 Android.mk 的修改内容，发现做了如下修改：
+# This forces a 64-bit build for Java6 +ifneq ($(filter 1.6%,$(java_version)),) + LOCAL_CFLAGS += -m64 + LOCAL_LDFLAGS += -m64 +endif