json c库的移植和使用

 移植

[root@mfr json-c-0.8]#tar –xzvf json-c-0.8.tar.gz

[root@mfr json-c-0.8]#cd json-c-0.8

[root@mfr json-c-0.8]#./configure CC= arm-unknown-linux-gnu-gcc –host=arm-unknown-linux –build=i686-pc-linux

checking for a BSD-compatible install... /usr/bin/install -c                                                               

checking whether build environment is sane... yes                                                                          

checking for a thread-safe mkdir -p... /bin/mkdir -p                                                                       

checking for gawk... gawk                                                                                                  

checking whether make sets $(MAKE)... yes                                                                                  

checking for arm-unknown-linux-strip... no       ---------应该是 arm-unknown-linux-gnu-strip                                                                          

checking for strip... strip                                                                                                

configure: WARNING: In the future, Autoconf will not detect cross-tools                                                    

whose name does not start with the host triplet.  If you think this                                                        

configuration is useful to you, please write to [email protected].                                                          

checking for style of include used by make... GNU                                                                          

checking for arm-unknown-linux-gcc... arm-unknown-linux-gnu-gcc                                                            

checking for C compiler default output file name... a.out                                                                  

checking whether the C compiler works... yes                                                                               

checking whether we are cross compiling... yes                                                                             

checking for suffix of executables...                                                                                      

checking for suffix of object files... o                                                                                   

checking whether we are using the GNU C compiler... yes                                                                    

checking whether arm-unknown-linux-gnu-gcc accepts -g... yes                                                               

checking for arm-unknown-linux-gnu-gcc option to accept ISO C89... none needed                                             

checking dependency style of arm-unknown-linux-gnu-gcc... gcc3                                                             

checking how to run the C preprocessor... arm-unknown-linux-gnu-gcc -E                                                     

checking for grep that handles long lines and -e... /bin/grep                                                              

checking for egrep... /bin/grep -E                                                                                         

checking for ANSI C header files... yes                                                                                    

checking for sys/types.h... yes                                                                                            

checking for sys/stat.h... yes                                                                                             

checking for stdlib.h... yes                                                                                               

checking for string.h... yes                                                                                               

checking for memory.h... yes                                                                                               

checking for strings.h... yes                                                                                              

checking for inttypes.h... yes                                                                                             

checking for stdint.h... yes                                                                                               

checking for unistd.h... yes                                                                                               

checking fcntl.h usability... yes                                                                                          

checking fcntl.h presence... yes                                                                                           

checking for fcntl.h... yes                                                                                                

checking limits.h usability... yes                                                                                         

checking limits.h presence... yes                                                                                          

checking for limits.h... yes                                                                                               

checking for strings.h... (cached) yes                                                                                     

checking syslog.h usability... yes                                                                                         

checking syslog.h presence... yes                                                                                          

checking for syslog.h... yes                                                                                               

checking for unistd.h... (cached) yes                                                                                      

checking sys/param.h usability... yes                                                                                      

checking sys/param.h presence... yes                                                                                       

checking for sys/param.h... yes                                                                                            

checking stdarg.h usability... yes                                                                                         

checking stdarg.h presence... yes                                                                                          

checking for stdarg.h... yes                                                                                               

checking for an ANSI C-conforming const... yes                                                                             

checking for size_t... yes                                                                                                 

checking for vprintf... yes                                                                                                

checking for _doprnt... no                                                                                                 

checking for working memcmp... no                                                                                          

checking for stdlib.h... (cached) yes                                                                                      

checking for GNU libc compatible malloc... no                                                                              

checking for stdlib.h... (cached) yes                                                                                      

checking for GNU libc compatible realloc... no                                                                             

checking for strndup... yes                                                                                                

checking for strerror... yes                                                                                               

checking for vsnprintf... yes                                                                                              

checking for vasprintf... yes                                                                                              

checking for open... yes                                                                                                   

checking for vsyslog... yes                                                                                                

checking for strncasecmp... yes                                                                                            

checking build system type... i686-pc-linux-gnu                                                                            

checking host system type... arm-unknown-linux-gnu                                                                         

checking for a sed that does not truncate output... ./configure: line 5419: echo: write error: Broken pipe                  

/bin/sed                                                                                                                   

checking for fgrep... /bin/grep -F                                                                                         

checking for ld used by arm-unknown-linux-gnu-gcc... /usr/local/arm/arm-unknown-linux-gnu/arm-unknown-linux-gnu/bin/ld      

checking if the linker (/usr/local/arm/arm-unknown-linux-gnu/arm-unknown-linux-gnu/bin/ld) is GNU ld... yes                 

checking for BSD- or MS-compatible name lister (nm)... no                                                                  

checking for arm-unknown-linux-dumpbin... no           ---没有此命令                                                                    

checking for arm-unknown-linux-link... no        ---没有此命令                                                                            

checking for dumpbin... no                                                                                                 

checking for link... link -dump -symbols                                                                                   

checking the name lister (link -dump -symbols) interface... BSD nm                                                         

checking whether ln -s works... yes                                                                                        

checking the maximum length of command line arguments... 1966080                                                           

checking whether the shell understands some XSI constructs... yes                                                          

checking whether the shell understands " ="... yes                                                                         

checking for /usr/local/arm/arm-unknown-linux-gnu/arm-unknown-linux-gnu/bin/ld option to reload object files... -r

checking how to recognize dependent libraries... pass_all

checking for arm-unknown-linux-ar... no     ---应该是arm-unknown-linux-gnu-ar

checking for ar... ar

checking for arm-unknown-linux-strip... strip    ---应该是arm-unknown-linux-gnu-strip

checking for arm-unknown-linux-ranlib... no    ---应该是arm-unknown-linux-gnu-ranlib

checking for ranlib... ranlib

checking command to parse link -dump -symbols output from arm-unknown-linux-gnu-gcc object... failed

checking for dlfcn.h... yes

checking for objdir... .libs

checking if arm-unknown-linux-gnu-gcc supports -fno-rtti -fno-exceptions... no

checking for arm-unknown-linux-gnu-gcc option to produce PIC... -fPIC -DPIC

checking if arm-unknown-linux-gnu-gcc PIC flag -fPIC -DPIC works... yes

checking if arm-unknown-linux-gnu-gcc static flag -static works... yes

checking if arm-unknown-linux-gnu-gcc supports -c -o file.o... yes

checking if arm-unknown-linux-gnu-gcc supports -c -o file.o... (cached) yes

checking whether the arm-unknown-linux-gnu-gcc linker (/usr/local/arm/arm-unknown-linux-gnu/arm-unknown-linux-gnu/bin/ld) supports shared libraries... yes

checking whether -lc should be explicitly linked in... no

checking dynamic linker characteristics... GNU/Linux ld.so

checking how to hardcode library paths into programs... immediate

checking whether stripping libraries is possible... yes

checking if libtool supports shared libraries... yes

checking whether to build shared libraries... yes

checking whether to build static libraries... yes

configure: creating ./config.status

config.status: creating Makefile

config.status: creating json.pc

config.status: creating config.h

config.status: executing depfiles commands

config.status: executing libtool commands

[root@mfr json-c-0.8]# make                                                                                                 

显示内容略

[root@mfr json-c-0.8]# make install

显示内容略

至此交叉编译完毕

json头文件将被安装在 /usr/local/include/json目录

交叉编译后的动态库文件被安装在 /usr/local/lib目录

编译json源码中自带的例子

[root@mfr json-c-0.8]##arm-unknown-linux-gnu-gcc –ljson –I/usr/local/include/json/ -L/usr/local/lib –o test2 test2.c –std=c99

出现undefined reference to “rpl_malloc”和undefined reference to “rpl_realloc”两处未定义错误，费了半天劲终于发现需要手动修改Makefile和config.h.in才能解决上面问题。

手动修改Makefile

1、 STRIP=arm-unknown-linux-gnu-strip

2、 AR= arm-unknown-linux-gnu-ar

3、 RANLIB= arm-unknown-linux-gnu-ranlib

手动修改config.h.in

屏蔽掉 

#undef malloc

#undef realloc

修改完上面两个文件，重新执行make和make install

编译json源码中自带的例子，交叉编译时一定要指定 -std=c99，为什么自己百度。。。

[root@mfr json-c-0.8]##arm-unknown-linux-gnu-gcc –ljson –I/usr/local/include/json/ -L/usr/local/lib –o test2 test2.c –std=c99

编译通过，此时在当前目录生成test2可执行文件

将/usr/local/lib目录下得libjson.*和pkgconfig目录都拷贝到ARM设备上得文件系统的/lib目录，

将test2拷贝到ARM设备上文件系统的/tmp目录，执行test2可得到正确结果。。。。。

至此json-c-0.8移植成功移植到arm系统，以后可以使用c语言编写的cgi返回JSON格式数据到客户端浏览器，浏览器使用javascript解析JSON数据，这样客户端浏览器和服务器端的数据传递方式清楚了。。。。

使用

1、json对象有几种类型       与常见的int ,char,double,boolean相对应。

 

 

2、json 有自己的数据类型 对于普通数据类型：int ,char,double,boolean,等 需要转换成 json自己的类型

json_object_new_string(const char *)  由char 转换成 自己的string类型 

json_object_new_string(double)  由double转换成 自己的double类型

。。。。。

3、json_object_put(json_object *) 释放json对象占据的内存。

要在代码所用功能完成后释放，也可以在json对象不被下文中的其他对象处理时，释放。否则出错。

最好的方法是在把结果传递给外面的值后，所有的json对象都没用了，一起释放。