bcraig added a comment.
> 1. A normal operating system target with a "hosted" libc.
> 2. A baremetal target with an "embedded" libc; basically a stripped down libc
> which only includes stuff that doesn't require an operating system. What
> exactly this includes varies; may include some form of "malloc", some "POSIX"
> APIs, semihosting, etc.
> 3. A baremetal target with no libc, using custom implementations for
> everything. This is what we conventionally referred to as "freestanding",
> and what -ffreestanding implements. The user provides memcpy/memmove/memset,
> and uses the compiler-provided "builtins" lib if neceessary, but nothing we
> would traditionally call "libc".
In my committee work, I'm targeting option 2. I think that's what should be
considered when talking about freestanding in a standards context.
Option 3 is valuable and should continue to exist, but it is non-conforming
pre-C23 and post-C23. The standards don't have any provision for requiring the
user to implement mem* functions that the implementation chooses to invoke
without the user ever spelling that function call (perhaps because they did
`char buf[256] = {0}` though). Post-C23, it doesn't provide enough. The C
library authors will likely need this mode to author the C library itself
though. I'll suggest calling this mode something like "nodefaultlibs".
Repository:
rG LLVM Github Monorepo
CHANGES SINCE LAST ACTION
https://reviews.llvm.org/D144889/new/
https://reviews.llvm.org/D144889
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