gcc - Do programming language compilers first translate to assembly or directly to machine code?

Question

I'm primarily interested in popular and widely used compilers, such as gcc. But if things are done differently with different compilers, I'd like to know that, too.

Taking gcc as an example, does it compile a short program written in C directly to machine code, or does it first translate it to human-readable assembly, and only then uses an (in-built?) assembler to translate the assembly program into binary, machine code -- a series of instructions to the CPU?

Is using assembly code to create a binary executable a significantly expensive operation? Or is it a relatively simple and quick thing to do?

(Let's assume we're dealing with only the x86 family of processors, and all programs are written for Linux.)

Answer 1

gcc actually produces assembler and assembles it using the as assembler. Not all compilers do this - the MS compilers produce object code directly, though you can make them generate assembler output. Translating assembler to object code is a pretty simple process, at least compared with compilation.

Some compilers produce other high-level language code as their output - for example, cfront, the first C++ compiler produced C as its output which was then compiled by a C compiler.

Note that neither direct compilation or assembly actually produce an executable. That is done by the linker, which takes the various object code files produced by compilation/assembly, resolves all the names they contain and produces the final executable binary.