一个GNU ld的问题

eclipse_2

我的程序分了几个文件夹
每个文件夹都有个makefile 每个下的makefile都用ld把该目录下多个.o连接成一个.o
我用的命令是ld -r -o A.o a.o b.o ... 生成A.o目标文件
然后在顶层的makefile把这些生成的.o 最终连接成可执行文件
我用的命令是ld -s -o exec A.o B.o
但是执行exec的时候出错了

然后我换了种方式 不在每个文件夹下用ld
而是只在顶层的makefile用了一次ld，把所有的.o连接成一个可执行文件
ld -s -o exec a.o b.o c.o ...
执行exec 成功了

想请教的是 为什么会这样的情况？
ld除了重定位数据和符号之外 还做了什么事情？

emmoblin

ld -s -o exec A.o B.o

是不是A.o B.o的目录没写对，多次使用ld一点问题都没有，而且是非常常用的。

eclipse_2

期待高手回答

EricFisher

是C程序？还是C++？ ld手册里提到了partial linking的问题：

-r
--relocatable
    Generate relocatable output—i.e., generate an output file that can in turn serve as input to ld. This is often called partial linking. As a side effect, in environments that support standard Unix magic numbers, this option also sets the output file's magic number to OMAGIC. If this option is not specified, an absolute file is produced. When linking C++ programs, this option will not resolve references to constructors; to do that, use `-Ur'.

    When an input file does not have the same format as the output file, partial linking is only supported if that input file does not contain any relocations. Different output formats can have further restrictions; for example some a.out-based formats do not support partial linking with input files in other formats at all.

ubuntuer

其实这种情况我一般都是
ar crs libA.a x.o xx.o ...
最后ld的时候
ld -o output y.o -lA

ubuntuer

ld后在ld确实没弄过
就像ar后再ar也是不行的一样^_^