到处都有多个定义错误，我该如何解决？答案

【问题标题】：Multiple Definitions error everywhere, how do I fix this?到处都有多个定义错误，我该如何解决？
【发布时间】：2020-07-24 16:14:55
【问题描述】：

这是我的 Makefile：

CC = gcc
SRC = $(wildcard src/*.c) \
          $(wildcard src/utils/*.c)
obj = $(SRC:.c=.o)

LDFLAGS =

output: $(obj)
        $(CC) $^ -o $@ $(LDFLAGS)

$(obj): $(SRC)
        $(CC) $^ -o $@ $(LDFLAGS)

.PHONY: clean
clean:
        rm -f $(obj) main

这是 main.c：

#include<stdio.h>
#include "utils/activations.h"

double check();

int main(){
        check();
}

double check(){
        double output = act(0.2, "sigmoid");
        return output;

}

这是activations.c：

#include<stdio.h>
#include<string.h>
#include<math.h>

double act();
double relu();
double sigmoid();
double tan_h();

double act(double x, char actFunc[]){
        double y;

        if(actFunc == "relu"){
                y = relu(x);
        }
        if(actFunc == "sigmoid"){
                y = sigmoid(x);
        }
        if(actFunc == "tanh"){
                y = tan_h(x);
        }

        return y;
}

double relu(double input){
        double output;
        if(input < 0){
                output = 0;
        } else{

                output = input;
        }
        return output;

}

double sigmoid(double  input){
        return 1/(1+exp(-1*input));
}

double tan_h(double input){
        return tanh(input);
}

好的，这是错误：

gcc src/main.c src/utils/activations.c -o src/utils/activations.o  
gcc src/main.o src/utils/activations.o -o output 
collect2: fatal error: ld terminated with signal 11 [Segmentation fault], core dumped
compilation terminated.
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/main.o: in function `mainCRTStartup':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: multiple definition of `mainCRTStartup'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../crt0.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/main.o: in function `mainCRTStartup':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: multiple definition of `WinMainCRTStartup'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../crt0.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/main.o:cygming-crtbegin.c:(.text+0x90): multiple definition of `__gcc_register_frame'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/main.o:cygming-crtbegin.c:(.text+0x150): multiple definition of `__gcc_deregister_frame'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0xc0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/main.o:cygming-crtbegin.c:(.data+0x4): multiple definition of `__dso_handle'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/crtbegin.o:cygming-crtbegin.c:(.data+0x4): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `mainCRTStartup':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: multiple definition of `mainCRTStartup'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../crt0.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `mainCRTStartup':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: multiple definition of `WinMainCRTStartup'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../crt0.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/crt0.c:21: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtbegin.c:(.text+0x90): multiple definition of `__gcc_register_frame'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtbegin.c:(.text+0x150): multiple definition of `__gcc_deregister_frame'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/crtbegin.o:cygming-crtbegin.c:(.text+0xc0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:main.c:(.text+0x180): multiple definition of `main'; src/main.o:main.c:(.text+0x180): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:main.c:(.text+0x199): multiple definition of `check'; src/main.o:main.c:(.text+0x199): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.text+0x1c0): multiple definition of `act'; src/main.o:activations.c:(.text+0x1c0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.text+0x21c): multiple definition of `relu'; src/main.o:activations.c:(.text+0x21c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.text+0x24b): multiple definition of `sigmoid'; src/main.o:activations.c:(.text+0x24b): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.text+0x274): multiple definition of `tan_h'; src/main.o:activations.c:(.text+0x274): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_crt0':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/cygwin_crt0.c:18: multiple definition of `cygwin_crt0'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/cygwin_crt0.c:18: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_premain0':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain0.c:13: multiple definition of `cygwin_premain0'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain0.c:13: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_premain1':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain1.c:13: multiple definition of `cygwin_premain1'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain1.c:13: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_premain2':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain2.c:13: multiple definition of `cygwin_premain2'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain2.c:13: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_premain3':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain3.c:13: multiple definition of `cygwin_premain3'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/premain3.c:13: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_crt0_common@8':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/_cygwin_crt0_common.cc:91: multiple definition of `_cygwin_crt0_common@8'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/_cygwin_crt0_common.cc:91: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_dll_entry@12':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/dll_entry.c:15: multiple definition of `_cygwin_dll_entry@12'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/dll_entry.c:15: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_noncygwin_dll_entry@12':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/dll_entry.c:15: multiple definition of `_cygwin_noncygwin_dll_entry@12'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/dll_entry.c:15: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `DllMain@12':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/dll_main.cc:35: multiple definition of `DllMain@12'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/dll_main.cc:35: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `pei386_runtime_relocator':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/pseudo-reloc-dummy.c:10: multiple definition of `_pei386_runtime_relocator'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/pseudo-reloc-dummy.c:10: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o: in function `cygwin_attach_dll':
/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/cygwin_attach_dll.c:19: multiple definition of `cygwin_attach_dll'; src/main.o:/usr/src/debug/cygwin-3.1.4-1/winsup/cygwin/lib/cygwin_attach_dll.c:19: first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.rdata+0x304): multiple definition of `__RUNTIME_PSEUDO_RELOC_LIST__'; src/main.o:activations.c:(.rdata+0x304): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtbegin.c:(.data+0x0): multiple definition of `_data_start__'; src/main.o:cygming-crtbegin.c:(.data+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtend.c:(.text+0x82c): multiple definition of `__DTOR_LIST__'; src/main.o:cygming-crtend.c:(.text+0x82c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x294): multiple definition of `__cxa_atexit'; src/main.o:fake:(.text+0x294): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x798): multiple definition of `free'; src/main.o:fake:(.text+0x798): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x108): multiple definition of `_nm___impure_ptr'; src/main.o:crt0.c:(.idata+0x108): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xc0): multiple definition of `_imp__tanh'; src/main.o:crt0.c:(.idata+0xc0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__tls_start__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.rdata+0x304): multiple definition of `_rt_psrelocs_start'; src/main.o:activations.c:(.rdata+0x304): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xa0): multiple definition of `_imp__cygwin_detach_dll'; src/main.o:crt0.c:(.idata+0xa0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xl_start__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xi_start__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xi_end__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.bss+0x20): multiple definition of `__dynamically_loaded'; src/main.o:activations.c:(.bss+0x20): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x800): multiple definition of `dll_dllcrt0'; src/main.o:fake:(.text+0x800): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x808): multiple definition of `GetModuleHandleA@4'; src/main.o:fake:(.text+0x808): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.bss+0x100): multiple definition of `hmod_libgcc'; src/main.o:activations.c:(.bss+0x100): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtbegin.c:(.bss+0x0): multiple definition of `_bss_start__'; src/main.o:cygming-crtbegin.c:(.bss+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.rdata+0x304): multiple definition of `__RUNTIME_PSEUDO_RELOC_LIST_END__'; src/main.o:activations.c:(.rdata+0x304): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.bss+0x1c): multiple definition of `environ'; src/main.o:activations.c:(.bss+0x1c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xac): multiple definition of `_imp__exp'; src/main.o:crt0.c:(.idata+0xac): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xd0): multiple definition of `_imp__GetProcAddress@8'; src/main.o:crt0.c:(.idata+0xd0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xp_start__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xp_end__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xb8): multiple definition of `_imp__posix_memalign'; src/main.o:crt0.c:(.idata+0xb8): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xc8): multiple definition of `_imp__FreeLibrary@4'; src/main.o:crt0.c:(.idata+0xc8): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x98): multiple definition of `_imp___impure_ptr'; src/main.o:crt0.c:(.idata+0x98): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xdc): multiple definition of `_IAT_end__'; src/main.o:crt0.c:(.idata+0xdc): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x790): multiple definition of `cygwin_internal'; src/main.o:fake:(.text+0x790): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.rdata+0x304): multiple definition of `_RUNTIME_PSEUDO_RELOC_LIST__'; src/main.o:activations.c:(.rdata+0x304): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.data+0x40): multiple definition of `_data_end__'; src/main.o:activations.c:(.data+0x40): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtend.c:(.text+0x820): multiple definition of `_CTOR_LIST__'; src/main.o:cygming-crtend.c:(.text+0x820): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.bss+0x104): multiple definition of `_bss_end__'; src/main.o:activations.c:(.bss+0x104): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xc_end__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x29c): multiple definition of `__main'; src/main.o:fake:(.text+0x29c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xc_start__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x7a8): multiple definition of `posix_memalign'; src/main.o:fake:(.text+0x7a8): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x238): multiple definition of `_lib32_libkernel32_a_iname'; src/main.o:crt0.c:(.idata+0x238): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtend.c:(.text+0x820): multiple definition of `__CTOR_LIST__'; src/main.o:cygming-crtend.c:(.text+0x820): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x780): multiple definition of `calloc'; src/main.o:fake:(.text+0x780): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.bss+0x18): multiple definition of `_fmode'; src/main.o:activations.c:(.bss+0x18): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x21c): multiple definition of `cygwin1_dll_iname'; src/main.o:crt0.c:(.idata+0x21c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x0): multiple definition of `_head_cygwin1_dll'; src/main.o:crt0.c:(.idata+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x90): multiple definition of `_imp____main'; src/main.o:crt0.c:(.idata+0x90): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x7b0): multiple definition of `realloc'; src/main.o:fake:(.text+0x7b0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xb4): multiple definition of `_imp__malloc'; src/main.o:crt0.c:(.idata+0xb4): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x788): multiple definition of `cygwin_detach_dll'; src/main.o:fake:(.text+0x788): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xa8): multiple definition of `_imp__dll_dllcrt0'; src/main.o:crt0.c:(.idata+0xa8): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x2a4): multiple definition of `exp'; src/main.o:fake:(.text+0x2a4): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xbc): multiple definition of `_imp__realloc'; src/main.o:crt0.c:(.idata+0xbc): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x8c): multiple definition of `_IAT_start__'; src/main.o:crt0.c:(.idata+0x8c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x94): multiple definition of `_imp___dll_crt0@0'; src/main.o:crt0.c:(.idata+0x94): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `_end__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xcc): multiple definition of `_imp__GetModuleHandleA@4'; src/main.o:crt0.c:(.idata+0xcc): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x7a0): multiple definition of `malloc'; src/main.o:fake:(.text+0x7a0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtend.c:(.text+0x82c): multiple definition of `_DTOR_LIST__'; src/main.o:cygming-crtend.c:(.text+0x82c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x8c): multiple definition of `_imp____cxa_atexit'; src/main.o:crt0.c:(.idata+0x8c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xt_start__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x9c): multiple definition of `_imp__calloc'; src/main.o:crt0.c:(.idata+0x9c): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xa4): multiple definition of `_imp__cygwin_internal'; src/main.o:crt0.c:(.idata+0xa4): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__tls_end__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.data+0x20): multiple definition of `__cygwin_cxx_malloc'; src/main.o:activations.c:(.data+0x20): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:fake:(.text+0x2ac): multiple definition of `tanh'; src/main.o:fake:(.text+0x2ac): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xb0): multiple definition of `_imp__free'; src/main.o:crt0.c:(.idata+0xb0): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:cygming-crtbegin.c:(.data+0x4): multiple definition of `__dso_handle'; /usr/lib/gcc/i686-pc-cygwin/9.3.0/crtbegin.o:cygming-crtbegin.c:(.data+0x4): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0x14): multiple definition of `_head_lib32_libkernel32_a'; src/main.o:crt0.c:(.idata+0x14): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.rdata+0x304): multiple definition of `_rt_psrelocs_end'; src/main.o:activations.c:(.rdata+0x304): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.idata+0xd4): multiple definition of `_imp__LoadLibraryA@4'; src/main.o:crt0.c:(.idata+0xd4): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:activations.c:(.rdata+0x304): multiple definition of `_RUNTIME_PSEUDO_RELOC_LIST_END__'; src/main.o:activations.c:(.rdata+0x304): first defined here
/usr/lib/gcc/i686-pc-cygwin/9.3.0/../../../../i686-pc-cygwin/bin/ld: src/utils/activations.o:crt0.c:(.rsrc+0x0): multiple definition of `__crt_xt_end__'; src/main.o:crt0.c:(.rsrc+0x0): first defined here
make: *** [Makefile:9: output] Error 1

我是 Makefile 新手，对 C 有点熟悉

【问题讨论】：

标签： c linux windows gcc makefile

【解决方案1】：

您忘记/忽略了编译目标文件。您在第一步获得可执行文件。所以你不需要规则$(obj): $(SRC)。

CC = gcc
SRC = $(wildcard src/*.c) \
          $(wildcard src/utils/*.c)
obj = $(SRC:.c=.o)

LDFLAGS =

output: $(SRC)
        $(CC) $^ -o $@ $(LDFLAGS)

.PHONY: clean
clean:
        rm -f $(obj) output

如果您想编译目标文件，请参见下文

CC = gcc
SRC = $(wildcard src/*.c) $(wildcard src/utils/*.c)
obj = $(SRC:.c=.o)

LDFLAGS =

output: $(obj)
        $(CC) $^ -o $@ $(LDFLAGS)

%.o: %.c $(SRC)
    $(CC) -c -o $@ $< $(CFLAGS)

.PHONY: clean
clean:
        rm -f $(obj) main

【讨论】：

非常感谢@SM，但是我很难理解，以下之间有什么区别：1.%.o: %.c 2.%.o: %.c $(SRC) 3.$(obj): $(SRC)谢谢，Syeam跨度>
1.你错过了-c（编译无链接）。 2.不能将多个文件编译成一个目标文件，所以每个.c都应该编译成一个.o文件。

【解决方案2】：

链接器告诉您，您对 X 的定义比您应该的要多，而您应该只有一个。在这种情况下，您必须跟踪可能定义这些附加定义的位置。在这个简单的项目中很简单，看看你用来编译和链接的命令：

output: $(obj)
        $(CC) $^ -o $@ $(LDFLAGS)

$(obj): $(SRC)
        $(CC) $^ -o $@ $(LDFLAGS)

在 gcc 中，您可以采用两种方式：

一步编译，另一步链接（这是你想要的），
在同一步骤中编译和链接（这是您实际所做的）。

您已在同一步骤中编译和链接两次。第一个目标 ($(obj): $(SRC)) 编译并链接您的可执行文件，然后您的第二个目标尝试链接已链接的内容。

您现在可以删除不必要的链接目标，或者在编译目标中告诉 gcc 您只想编译文件，因为稍后您将链接它们（-c 标志）。

单独编译和链接

CC = gcc
SRC = $(wildcard src/*.c) $(wildcard src/utils/*.c)
obj = $(SRC:.c=.o)

LDFLAGS =

output: $(obj)
        $(CC) $^ -o $@ $(LDFLAGS)

$(obj): $(SRC)
        $(CC) -c $^

.PHONY: clean
clean:
        rm -f $(obj) main

一次编译链接

CC = gcc
SRC = $(wildcard src/*.c) $(wildcard src/utils/*.c)
obj = $(SRC:.c=.o)

LDFLAGS =

output: $(SRC)
        $(CC) $^ -o $@ $(LDFLAGS)

.PHONY: clean
clean:
        rm -f $(obj) main

【讨论】：