编译C源代码时（不兼容的库）找不到-lagent

Question

With gcc in ubuntu I used this command to compile my source code:

gcc 1.c -L. -lagent -lm -lpthread -o 1

but I got this error:

/usr/bin/ld: skipping incompatible ./libagent.so when searching for -lagent
/usr/bin/ld: cannot find -lagent
collect2: ld returned 1 exit status

How can I solve this?

Answer 1

The linker is telling you that the file ./libagent.so exists, but isn't in the appropriate format .

It could be an empty file, or built for 32-bit instead of 64-bit, or it could be a symlink pointing to the wrong version.

Answer 2

Let's look at your command line parameters first.

gcc 1.c -L. -lagent -lm -lpthread -o 1

You call the compiler gcc with the input source code of 1.c and then you specify an additional (link) library path to include the current directory ( . ) -L. . Then you tell it to link against the agent and pthread libraries, where shared (dynamic) libraries have the default name format of libNAME.so where NAME is replaced with the name. Static libraries have the default file extension .a (from the term archive ). Then you specify the output (executable in this case) to be the file 1 (digit one, not the letter 'ell').

/usr/bin/ld: skipping incompatible ./libagent.so when searching for -lagent

This is the linker ( ld ) telling you that the file ./libagent.so (it found presumably in the current directory) is not a valid shared library format as it was expecting. This could be for a different machine architecture (x86-64, ARMle, PowerPC, MIPS) or a incompatible library format (I don't know if library files, .so, have any COFF or ELF or PE dependencies or not). Or simply otherwise empty or corrupted (eg interrupted output due to errors compiling / linking).

So you normally want to not include your current directory in your linker's search path, unless you have the copy of the library that you have not yet installed (typically to /usr/lib/ or /usr/local/lib/), such as you wrote the library and wish to link test programs to it before you install it.

Debian and Unbuntu-oriented part of the answer:

Normally you want to install shared library's runtime component (often named something like libagent ) and the associated development files (most often at least a header file and hopefully a manpage) in the format libagent-dev . RPM based Linux systems use libagent-devel style naming conventions (from memory). So sudo aptitude install libagent-dev should do the trick if that is the package's name.