undefined reference to `WinMain@16' collect2.exe: error: ld returned 1 exit status

Question

I am using eclipse CDT to test the Intel instructions and below is my program:

#define cpuid(func,ax,bx,cx,dx)\
__asm__ __volatile__ ("cpuid":\
 "=a" (ax), "=b" (bx), "=c" (cx), "=d" (dx) : "a" (func));
int Check_CPU_support_AES()
 {
 unsigned int a,b,c,d;
 cpuid(1, a,b,c,d);
 return (c & 0x2000000);
 }

When I compile the above code, I get linkage error as:

Info: Internal Builder is used for build
gcc -O0 -g3 -Wall -c -fmessage-length=0 -o "src\\Intel.o" "..\\src\\Intel.c" 
gcc -o Intel.exe "src\\Intel.o" 
c:/mingw/bin/../lib/gcc/mingw32/4.7.2/../../../libmingw32.a(main.o):main.c:(.text.startup+0xa7): undefined reference to `WinMain@16'
collect2.exe: error: ld returned 1 exit status

Please help me regarding the issue.

Solution 1

Your program isn't complete. You need to implement the OS-expected entry point. In your case, that looks like it's called WinMain.

Solution 2

Yes, Main () function is missing and the compiler is not able to find an entry point for executing the program.

One more reason is even if you have written the main function but if you didnot save the .cpp file and try to compile it will give the same error.So make sure you have successfully saved the .cpp file and then compile and run your code.

Hope this will help since I have faced similar issue and I spent around hours to figure it out , Thanks

Solution 3

1. The main() function is missing.
2. Save as this code as some new file. Again run to compile the code.
3. Check the PATH environment variable.

Solution 4

In VS Code, this can happen when you haven't saved your code. Click Ctrl + s to save the code and then run the program again.

Or to make this happen automatically, go to Settings and search for "save". Scroll down and search for "Whether to save the current file before running" and enable it.

Solution 5

you have to save the file first>> Ctrl + s

View more solutions

Comments

[annunarcist]

Yes, I figured it out. I need to implement main(). Thank You.

[peterh]

I am not sure that this would be the cause. WinMain wants to be compiled in a GUI program, for console programs, there is only simple main().

[Raahim Fareed]

Somehow this worked for me, compiling file.cpp was giving me this error but when I copied the same code into another file index.cpp and compiled it. It worked just fine. My code was just the iostream header, main function and a cout statement for "hello world"

[Peter Cordes]

I'm guessing the args have to be exact so the @16 decoration (number of bytes to pop for __stdcall functions) will match what CRT is looking for. Callee-pops depends on the callee declaring its args exactly.

[Zircoz]

Your innocent answer is underestimated xD

[Peter Cordes]

@JanakaEkanayake - You significantly changed this answer. It was talking about some kind of auto-save option that automatically triggers before build / run, but you changed it to only talking about manually saving with a keyboard shortcut. Unless you know that there's no such feature, that's not a good edit. (The original could use some cleanup, but not changing the key point.)

[INDRAJITH EKANAYAKE]

@PeterCordes I agree with you thanks for the correction

[Peter Cordes]

Multiple existing answers already say this, including one mentioning ctrl + s. Please don't post "me too" answers; upvote an existing answer that worked for you.

[Admin]

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