On 16/07/2021 01:21, Mark Millard via freebsd-toolchain wrote:
Context:
# uname -apKU
FreeBSD CA72_16Gp_ZFS 14.0-CURRENT FreeBSD 14.0-CURRENT #10
main-n247756-348c41d1815d-dirty: Mon Jul 5 10:23:55 PDT 2021
root@CA72_16Gp_ZFS:/usr/obj/BUILDs/main-CA72-nodbg-clang/usr/main-src/arm64.aarch64/sys/GENERIC-NODBG-CA72
arm64 aarch64 1400025 1400025
Showing a trivial example . . .
# cat trivial.cpp
// # c++ -v -o trival trivial.cpp
int main() {
}
# c++ -v
FreeBSD clang version 12.0.1 ([email protected]:llvm/llvm-project.git
llvmorg-12.0.1-rc2-0-ge7dac564cd0e)
Target: aarch64-unknown-freebsd14.0
Thread model: posix
InstalledDir: /usr/bin
# c++ -v -o trivial trivial.cpp
FreeBSD clang version 12.0.1 ([email protected]:llvm/llvm-project.git
llvmorg-12.0.1-rc2-0-ge7dac564cd0e)
Target: aarch64-unknown-freebsd14.0
Thread model: posix
InstalledDir: /usr/bin
"/usr/bin/c++" -cc1 -triple aarch64-unknown-freebsd14.0 -emit-obj -mrelax-all
--mrelax-relocations -disable-free -disable-llvm-verifier -discard-value-names
-main-file-name trivial.cpp -mrelocation-model static -mframe-pointer=non-leaf
-fno-rounding-math -mconstructor-aliases -munwind-tables -target-cpu generic
-target-feature +neon -target-abi aapcs -fallow-half-arguments-and-returns
-fno-split-dwarf-inlining -debugger-tuning=gdb -v -resource-dir /usr/lib/clang/12.0.1
-internal-isystem /usr/include/c++/v1 -fdeprecated-macro -fdebug-compilation-dir
/usr/home/root/c_tests -ferror-limit 19 -fno-signed-char -fgnuc-version=4.2.1
-fcxx-exceptions -fexceptions -faddrsig -o /tmp/trivial-5d90b5.o -x c++ trivial.cpp
clang -cc1 version 12.0.1 based upon LLVM 12.0.1 default target
aarch64-unknown-freebsd14.0
#include "..." search starts here:
#include <...> search starts here:
/usr/include/c++/v1
/usr/lib/clang/12.0.1/include
/usr/include
End of search list.
"/usr/local/bin/aarch64-unknown-freebsd14.0-ld" --eh-frame-hdr
-dynamic-linker /libexec/ld-elf.so.1 --enable-new-dtags -o trivial /usr/lib/crt1.o
/usr/lib/crti.o /usr/lib/crtbegin.o -L/usr/lib /tmp/trivial-5d90b5.o -lc++ -lm -lgcc
--as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed
/usr/lib/crtend.o /usr/lib/crtn.o
CA72_16Gp_ZFS# c++ -v
FreeBSD clang version 12.0.1 ([email protected]:llvm/llvm-project.git
llvmorg-12.0.1-rc2-0-ge7dac564cd0e)
Target: aarch64-unknown-freebsd14.0
Thread model: posix
InstalledDir: /usr/bin
Note the "/usr/local/bin/aarch64-unknown-freebsd14.0-ld" path
for ld.
I've an example where this usage leads to:
/usr/local/bin/aarch64-unknown-freebsd14.0-ld: /usr/bin/../lib/LLVMgold.so: error loading
plugin: Cannot open "/usr/bin/../lib/LLVMgold.so"
clang++: error: linker command failed with exit code 1 (use -v to see
invocation)
This is the documented behaviour for clang when cross-compiling. You
can specify a target in one of two ways with clang:
- Via the -target flag.
- By invoking clang with a symlink named {target}-clang[++]
Clang will look for all of the tools in your path (or in the tree
specified with -B if you provide an alternative location for tools). If
clang finds {target}-{tool name} then it will invoke this in preference
to {tool name}. This avoids situations where, for example, your system
ld is BFD ld (or any other linker that doesn't support cross-linking)
and you are cross compiling.
In general, if you are cross building anything and not specifying
--sysroot (to tell it where to find headers and libraries for the
target) and -B (to tell it where to find tools) then you are probably
doing something wrong.
David
