尝试使用clang编译代码时出错

Question

我正在运行Ubuntu 18.04。我正在尝试编译llvm代码，使用：llc-7 prog.ll -o prog.s然后clang-7 prog.s lib.a -o prog.exe。如果您认为有帮助，我可以提供任何代码。我非常肯定库lib.a的有效性。我也尝试过clang版本6。 当运行clang时，使用-v参数我得到：

clang version 7.1.0-svn353565-1~exp1~20190406090509.61 (branches/release_70)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.3.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
 "/usr/lib/llvm-7/bin/clang" -cc1as -triple x86_64-pc-linux-gnu -filetype obj -main-file-name prog.s -target-cpu x86-64 -fdebug-compilation-dir /home/john/github/Compiler-Alan/LLVM/alan -dwarf-debug-producer clang version 7.1.0-svn353565-1~exp1~20190406090509.61 (branches/release_70) -dwarf-version=4 -mrelocation-model static -o /tmp/prog-38284d.o prog.s
 "/usr/bin/ld" -z relro --hash-style=gnu --build-id --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o prog.exe /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu/crt1.o /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu/crti.o /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/crtbegin.o -L/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0 -L/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../.. -L/usr/lib/llvm-7/bin/../lib -L/lib -L/usr/lib /tmp/prog-38284d.o lib.a -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/crtend.o /usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu/crtn.o
/usr/bin/../lib/gcc/x86_64-linux-gnu/7.3.0/../../../x86_64-linux-gnu/crt1.o: In function `_start':
(.text+0x20): undefined reference to `main'
clang: error: linker command failed with exit code 1 (use -v to see invocation)

到目前为止谷歌搜索并没有帮助我。你有什么建议吗？ 如果我需要澄清任何内容或提供更多信息，请通知我。

Answer 1

问题是我没有在LLVM代码中指定一个main函数。感谢@Mike Kinghan。