编译C程序时无法链接到Rust编译的库

Question

I have been trying to compile and run a minimal example of calling a Rust function from C. However, I keep getting a linker error:

$ gcc -L . test.c -ltest
C:\Users\...\AppData\Local\Temp\ccWuOBbj.o:test.c:(.text+0x16): undefined reference to `squared'
collect2.exe: error: ld returned 1 exit status

The C code:

#include <stdio.h>

int squared(int);

int main() {
    printf("5 * 5 = %d", squared(5));
    return 0;
}

The Rust code:

#![no_std]
#![feature(lang_items)]

extern crate core;

#[lang = "stack_exhausted"] extern fn stack_exhausted() {}
#[lang = "eh_personality"] extern fn eh_personality() {}
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }

#[no_mangle]
pub extern "C" fn squared(x: isize) -> isize {
    x * x
}

I am compiling the Rust code with rustc --crate-type staticlib -o libtest.a test.rs

Some details:

• Windows 8 x64
• Rustc version: 1.0.0-nightly (4e4e8cff1 2015-01-24 22:14:14 +0000)
• GCC version: 4.8.1
• Output of DUMPBIN /SYMBOLS

Answer 1

Put "-ltest" after "test.c". ld only links in required parts of library archives, and doesn't know squared() is required until it sees the .o file generated from test.c, at which time libtest.a has already been linked earlier when no functions were yet required from it.