Ruby代码
require'mkmf'create_makefile("string_hack");
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执行ruby extconf.rb，将产生一个Makefile，执行make，生成一个string_hack.so的链接库。扩展写完了，通过ruby调用：
Ruby代码
require'string_hack"t=Test.new(1..3).each{|i|t.test}
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输出：
before concat: str:0x40098a40, str.aux.shared:0x3, str.ptr:str
after concat: str:0x40098a40, str.aux.shared:0x8, str.ptr:string
before concat: str:0x40098a2c, str.aux.shared:0x3, str.ptr:str
after concat: str:0x40098a2c, str.aux.shared:0x8, str.ptr:string
before concat: str:0x40098a18, str.aux.shared:0x3, str.ptr:str
after concat: str:0x40098a18, str.aux.shared:0x8, str.ptr:string
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从结果可以看出，在str concat之前之后，str指向的位置没有改变，改变的仅仅是str中ptr指向的字符串的值，看看rb_str_cat2函数的实现就一目了然了：
cpp代码
VALUErb_str_cat(str,ptr,len)VALUEstr;
constchar*ptr;
longlen;
{
if(len<0){rb_raise(rb_eArgError,"negativestringsize(orsizetoobig)");
}
if(FL_TEST(str,STR_ASSOC))
{
rb_str_modify(str);
REALLOC_N(RSTRING(str)->ptr,char,RSTRING(str)->len+len);
memcpy(RSTRING(str)->ptr+RSTRING(str)->len,ptr,len);
RSTRING(str)->len+=len;
RSTRING(str)->ptr[RSTRING(str)->len]='"0';
/*sentinel*/
returnstr;
}
returnrb_str_buf_cat(str,ptr,len);
}
VALUErb_str_cat2(str,ptr)VALUEstr;
constchar*ptr;
{
returnrb_str_cat(str,ptr,strlen(ptr));
}
//string.c
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