https://bugs.llvm.org/show_bug.cgi?id=51223
Bug ID: 51223
Summary: AVR driver can't find avr-libc in /opt/local/avr/
Product: clang
Version: unspecified
Hardware: Macintosh
OS: MacOS X
Status: NEW
Severity: normal
Priority: P
Component: Driver
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected],
[email protected]
$ clang -v
clang version 13.0.0 (https://github.com/llvm/llvm-project.git
4e52a04833fb352090498d6d1c013a2c61d75e53)
A common AVR toolchain setup on macOS is to use /opt/local/ as the "prefix" and
/opt/local/avr/ as the "sysroot" where the headers and libraries live. Under
this scheme:
* avr-gcc lives at /opt/local/bin/avr-gcc (the cc1s live in
/opt/local/libexec/gcc/...),
* the AVR binutils live in /opt/local/avr/bin/ (hardlinked to avr-prefixed
versions in /opt/local/bin/), and
* avr-libc (including the crt0s) lives in /opt/local/avr/lib/.
In clang 13.0.0, I can't find any way to get the driver to link an AVR program
with this setup. I'm using (see NOTE below):
$ clang -v -o build/foo -mmcu=atmega644p -target avr --sysroot /opt/local/ -I
'=avr/include' build/foo.o
which produces
clang-13: warning: no avr-libc installation can be found on the system, cannot
link standard libraries [-Wavr-rtlib-linking-quirks]
clang-13: warning: standard library not linked and so no interrupt vector table
or compiler runtime routines will be linked [-Wavr-rtlib-linking-quirks]
followed by the expected linker failures because libc is missing.
I think I tracked this down to the fact that `PossibleAVRLibcLocations` (in
Driver/ToolChains/AVR.cpp) consists of "/usr/avr" and "/usr/lib/avr", neither
of which (even when prepended with the given `--sysroot`) is a directory that
exists.
If I add simply "avr" to that array, things work great. But as far as I know
there's no way to control that without rebuilding clang.
===
NOTE: In that clang invocation above, I *believe* it would be more correct for
me to use
--sysroot /opt/local/avr/ -I '=include'
If I do that, however, I get a different weird warning (notice it's complaining
about `avr-gcc`, not avr-libc):
clang: warning: no avr-gcc installation can be found on the system, cannot link
standard libraries [-Wavr-rtlib-linking-quirks]
I don't understand this warning -- surely clang shouldn't need to invoke
`avr-gcc` itself, right? Why would knowing where `avr-gcc` is be important to
find the avr-libc libraries?
In any case, the `PossibleAVRLibcLocations` situation described above means
that the driver tries looking for avr-libc in /opt/local/avr/usr/avr and
/opt/local/avr/usr/lib/avr, neither of which exist.
===
Patch I used to make my setup work, for posterity:
diff --git a/clang/lib/Driver/ToolChains/AVR.cpp
b/clang/lib/Driver/ToolChains/AVR.cpp
index ea35abb86f45..85edf905dcc7 100644
--- a/clang/lib/Driver/ToolChains/AVR.cpp
+++ b/clang/lib/Driver/ToolChains/AVR.cpp
@@ -298,6 +298,7 @@ llvm::Optional<unsigned> GetMCUSectionAddressData(StringRef
MCUName) {
}
const StringRef PossibleAVRLibcLocations[] = {
+ "/avr",
"/usr/avr",
"/usr/lib/avr",
};
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