链接库与 arm gcc

Question

I'm getting an issue with my embedded c project.

I'm trying to link libcrc to my project, but I'm getting an undefined reference error.

I tried boiling the problem down to its simplest form and this is what I have:

#include "checksum.h"
int main(void)
{
  char data[8];
  short a = crc_modbus(data, 8);
  while (1);
}

Then I run this command:

arm-none-eabi-gcc -mcpu=arm7tdmi --specs=nosys.specs -I../../../libraries/libcrc/include -o main ../src/main.c -L../../../libraries/libcrc/lib -lcrc

and I get the following error:

/var/folders/_8/_cw6l3nd335f_j6cn6z79m4m0000gn/T//ccL0dSgt.o: In function `main':
main.c:(.text+0x18): undefined reference to `crc_modbus'
collect2: error: ld returned 1 exit status

I read about how the flags' order matters, and I've played around with the order to no avail.

I've also tried running the following:

gcc -I../../../libraries/libcrc/include ../src/main.c -lcrc -o main -L../../../libraries/libcrc/lib

And I got this as the output:

../src/main.c:5:24: warning: passing 'char [8]' to parameter of type 'const unsigned char *' converts between pointers to integer types with different sign [-Wpointer-sign]
  short a = crc_modbus(data, 8);
                       ^~~~
../../../libraries/libcrc/include/checksum.h:93:52: note: passing argument to parameter 'input_str' here
uint16_t                crc_modbus(         const unsigned char *input_str, size_t num_bytes       );
                                                                 ^
1 warning generated.

So it seems when I pass essentially the same command to gcc as to arm-gcc it works. What am I missing here? What needs to be added arm gcc

Answer 1

From the comment that it works for gcc but it's not working for arm-gcc , it looks like you are using a cross-compiler and you are picking up the libraries for the host architecture instead of the libraries for the target architecture.

When you are using a crosscospiler, you need to make sure that your toolchain environment is properly set, otherwise you will have lot's of problems with the build. Also you need to assure that the libraries which are available your build environment are build for the target architecture. If not, the linker will find the library specified with -L , but inside the library there will be no symbols for your target architecture, so you will get error that the symbols you are using form that library are missing.