[llvm-bugs] [Bug 25185] New: -nostdlib -rtlib=compiler_rt fails, no mechanism to link libc.so

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=25185

            Bug ID: 25185
           Summary: -nostdlib -rtlib=compiler_rt fails, no mechanism to
                    link libc.so
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Driver
          Assignee: unassignedclangbugs at nondot.org
          Reporter: nsz at port70.net
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

-rtlib is ignored after -nostdlib:

$ clang -nostdlib -rtlib=compiler-rt t.c -o t
clang-3.6: warning: argument unused during compilation: '-rtlib=compiler-rt'
$ clang --version
clang version 3.6.2 (tags/RELEASE_362/final)
Target: armv6-alpine-linux-muslgnueabihf

this makes it impossible to link libc.so which must use -nostdlib,
but has to be linked against the right compiler runtime.

there seems to be no way to discover (e.g. in a configure script) how to
link to the right clang compiler runtime (this is most likely necessary
for other freestanding code too, not just the c runtime).

(the problem persists on trunk and target independent.)

on gcc one can use either of

gcc -nostdlib t.c -lgcc
gcc -nostdlib t.c `gcc -print-file-name=libgcc.a`

clang should either accept -rtlib or needs a similar mechanism
to -print-file-name, in fact there are patches proposed along
those lines:

http://reviews.llvm.org/D10049
http://reviews.llvm.org/D10050
http://reviews.llvm.org/D10051
http://reviews.llvm.org/D10052

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