Changing array values in C produces "undefined reference to 'memset'" [closed] - arrays

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I am initializing a 32-element array of 1s and 0s for the starting state for a Game of Life in C. When I use this line:
int board[] = {0, 1, 1, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 1,
0, 0, 1, 0, 0, 1, 1, 1, 0, 1, 0, 0, 1, 1, 1, 0};
there are no issues compiling. However, when I simply change the values in the array, and not the length or declaration of the array:
int board[] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
the code does not compile, instead producing an "undefined reference to 'memset.'". Here is the error I get when compiling:
[ubuntu#swell-dipper:~/OS/assiqnment2/c-and-assemblvA] $ make
riscv64-unknown-elf-gcc -O -march=rv32im -mabi=ilp32 -g -c main.c -o main.o
riscv64-unknown-elf-gcc -O -march=rv32im -mabi=ilp32 -g -c lib.c -o lib.o
riscv64-unknown-elf-as -march=rv32im -g -c calc_val.s -o calc_val.o
riscv64-unknown-elf-gcc -O -march=rv32im -mabi.ilp32 -g -c simulation.c \
-o simulation.o
riscv64-unknown-elf-ld -nostdlib -o simulation -Map simulation.map \
-T demo.lds crt0.0 main.o lib.o calc_val.o simulation.o
riscv64-unknown-elf-ld: main.o: in function 'main':
/home/ubuntu/OS/assignment2/c-and-assembly/q2/main.c:23:
undefined reference to 'memset'
make: *** [Makefile:58: simulation] Error 1
How could the same exact code, simply with different values for the elements of the array, not be able to be compiled? I also never use anything in regards to memset in the code anywhere.
I have tried a few different values for the elements of the array, and it is on and off whether or not the code compiles.

Answer 1

You're running ld yourself. This is almost always a mistake. Use the gcc "compiler driver" to link, and remove -nostdlib and crt0.o from the linking command line, and the problem should go away.
What's happening is that the compiler has probably chosen to generate code for the second array initialization as if you had written
int board[32];
memset(board, 0, sizeof board);
board[K] = 1;
where K is the position of that single 1 in your array initializer. This is perfectly permissible; the C standard says that the compiler is allowed to generate calls to any C library function, even if they did not appear in the source code. You can make GCC less inclined to do this by using the -ffreestanding command line option, but it will not completely eliminate these "synthetic" calls. Section 2.1 of GCC's manual specifically points out that even in -ffreestanding mode, it may generate calls to memcpy, memmove, memset and memcmp.
GCC may also generate calls to functions in its own internal runtime library, whether or not it's in freestanding mode. These are used for things like arithmetic operations that the hardware doesn't provide instructions for.
When you use the compiler driver to link, the C library, the internal runtime library, and some "startup files" that handle stuff like C++ global constructors are automatically included in the link, so all this is invisible to you. Using ld bypasses that and exposes the fact that code generation needs these things even if you think it doesn't. You can in principle use gcc -v to find the names of all the extra implicit stuff and add back only the bits you need, but it's almost certainly easier to just use the compiler driver to link.