I am running Ubuntu 18.04. I am trying to compile an llvm code, using: llc-7 prog.ll -o prog.s and then clang-7 prog.s lib.a -o prog.exe. I can provide any piece of code if you think that will help. I am pretty certain for the validity of the library lib.a. I have also tried clang version 6.
When running clang, using the -v parameter i get:
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)
So far googling has not helped me. Do you have any suggestions?
Inform me if I need to clarify anything or provide more information.
The problem was that I hadn't specified a main function inside the LLVM code. Thanks to @Mike Kinghan.