Linking your compiled applications with IBM Open XL C/C++

The linker links specified object files to create one executable file.

All invocation commands call both the compiler and the linker by default unless you specify one of the following compiler options:
  • -c
  • -E
  • -S
  • -fsyntax-only
  • -###
  • --help
  • --version
For example, you can use ibm-clang++_r to compile file1.C and file3.C to produce object files file1.o and file3.o; after that, all object files, including file2.o, are submitted to the linker to produce one executable.
ibm-clang++_r file1.C file2.o file3.C

Valid input and output files

Input files
Object files, unstripped executable files, and library files serve as input to the linker. Object files must have a .o suffix, for example, filename.o. Library file names have a .a or .so suffix, for example, filename.a, or filename.so..
Output files
The linker generates an executable file and places it in your current directory. The default name for an executable file is a.out. To name the executable file explicitly, use the -o file_name option with the compiler invocation command, where file_name is the name you want to give to the executable file. For example, to compile myfile.c and generate an executable file called myfile, enter: 
ibm-clang myfile.c -o myfile
If you use the -shared option to create a shared library, the default name of the shared object created is shr.o. You can use the -o option to rename the file and give it a .so suffix.

How to compile without linking

By default, an invocation command calls both the compiler and the linker. It accepts all linker options and passes linker options to the linker. To compile source files without linking, use the -c compiler option. The -c option stops the compiler after compilation is completed and produces output, an object file file_name.o for each file_name.nnn input source file, unless you use the -o option to specify a different object file name. You can link the object files later using the same invocation command, specifying the object files without the -c option.

For example, you can use the -c option to produce the object files for file1.C, file2.C, and file3.C. The object files can be linked later with ibm-clang++_r.

ibm-clang++_r -c file1.C               # Produce one object file (file1.o)
ibm-clang++_r -c file2.C file3.C       # Or multiple object files (file1.o, file3.o)
ibm-clang++_r file1.o file2.o file3.o  # Link object files with default libraries

How to invoke the linker explicitly

You can invoke the linker explicitly with the ld command. However, the compiler invocation commands set several linker options, and link some standard files into the executable output by default. In most cases, it is better to use one of the compiler invocation commands to link your object files.