Add cpp flag to cc

[cchalmers]

This means that clang++ will be called instead of clang.

This was causing me issueing when trying to use the nix version of clang, not sure why.

[dtolnay]

Could you share the error message without this change?

[cchalmers]

[nix-shell:~/Documents/rust/cxx]$ cargo build
   Compiling cc v1.0.52
   Compiling proc-macro2 v1.0.12
   Compiling unicode-xid v0.2.0
   Compiling syn v1.0.19
   Compiling link-cplusplus v1.0.1
   Compiling cxx v0.3.1 (/Users/chris/Documents/rust/cxx)
   Compiling quote v1.0.4
error: failed to run custom build command for `cxx v0.3.1 (/Users/chris/Documents/rust/cxx)`

Caused by:
  process didn't exit successfully: `/Users/chris/Documents/rust/cxx/target/debug/build/cxx-4c4a7f6743abc4bf/build-script-build` (exit code: 1)
--- stdout
TARGET = Some("x86_64-apple-darwin")
OPT_LEVEL = Some("0")
HOST = Some("x86_64-apple-darwin")
CC_x86_64-apple-darwin = None
CC_x86_64_apple_darwin = None
HOST_CC = None
CC = Some("clang")
CFLAGS_x86_64-apple-darwin = None
CFLAGS_x86_64_apple_darwin = None
HOST_CFLAGS = None
CFLAGS = None
CRATE_CC_NO_DEFAULTS = None
DEBUG = Some("true")
running: "clang" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-fno-omit-frame-pointer" "--target=x86_64-apple-darwin" "-Wall" "-Wextra" "-std=c++11" "-o" "/Users/chris/Documents/rust/cxx/target/debug/build/cxx-4acf56ca7a4f0206/out/src/cxx.o" "-c" "src/cxx.cc"
cargo:warning=In file included from src/cxx.cc:1:
cargo:warning=src/../include/cxx.h:2:10: fatal error: 'array' file not found
cargo:warning=#include <array>
cargo:warning=         ^~~~~~~
cargo:warning=1 error generated.
exit code: 1

--- stderr


error occurred: Command "clang" "-O0" "-ffunction-sections" "-fdata-sections" "-fPIC" "-g" "-fno-omit-frame-pointer" "--target=x86_64-apple-darwin" "-Wall" "-Wextra" "-std=c++11" "-o" "/Users/chris/Documents/rust/cxx/target/debug/build/cxx-4acf56ca7a4f0206/out/src/cxx.o" "-c" "src/cxx.cc" with args "clang" did not execute successfully (status code exit code: 1).



warning: build failed, waiting for other jobs to finish...
error: build failed

[dtolnay]

Thanks -- I asked because cpp(true) has two effects as far as I could tell, it calls clang++ rather than clang, but it also adds some link flags determined based on the target. From your error message it looks like only the first effect is the relevant one, and we're clear to continue delegating the link flags to the link-cplusplus crate for configurability.

Would you be able to confirm that 110df7d still solves the error in your environment?

[cchalmers]

Yep, still works for me with your change.

[dtolnay]

Nice. Thanks for checking and thanks for the PR!

[dtolnay]

I published 0.3.2 with this fix.