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Compiler

Compiler driver

It is a wrapper around the executables included in the process of calling the individual component. Some examples are clang and gcc.

// TODO: put diagram of the process.

To see the subsequent calls made by the compiler driver, verbose mode can reveal -v more information. For example: $ clang -v hello.c ($ clang -v -### hello.c for a dry run).

 "/usr/lib/llvm-14/bin/clang" -cc1 -triple x86_64-pc-linux-gnu -emit-obj -mrelax-all --mrelax-relocations -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name hello.c -mrelocation-model pic -pic-level 2 -pic-is-pie -mframe-pointer=all -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -mllvm -treat-scalable-fixed-error-as-warning -debugger-tuning=gdb -v -fcoverage-compilation-dir=/home/maverick/experiments -resource-dir /usr/lib/llvm-14/lib/clang/14.0.0 -internal-isystem /usr/lib/llvm-14/lib/clang/14.0.0/include -internal-isystem /usr/local/include -internal-isystem /usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include -internal-externc-isystem /usr/include/x86_64-linux-gnu -internal-externc-isystem /include -internal-externc-isystem /usr/include -fdebug-compilation-dir=/home/maverick/experiments -ferror-limit 19 -fgnuc-version=4.2.1 -fcolor-diagnostics -faddrsig -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o /tmp/hello-e13d0b.o -x c hello.c
clang -cc1 version 14.0.0 based upon LLVM 14.0.0 default target x86_64-pc-linux-gnu
ignoring nonexistent directory "/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../x86_64-linux-gnu/include"
ignoring nonexistent directory "/include"
#include "..." search starts here:
#include <...> search starts here:
 /usr/lib/llvm-14/lib/clang/14.0.0/include
 /usr/local/include
 /usr/include/x86_64-linux-gnu
 /usr/include
End of search list.
 "/usr/bin/ld" -pie -z relro --hash-style=gnu --build-id --eh-frame-hdr -m elf_x86_64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 -o out /lib/x86_64-linux-gnu/Scrt1.o /lib/x86_64-linux-gnu/crti.o /usr/bin/../lib/gcc/x86_64-linux-gnu/11/crtbeginS.o -L/usr/bin/../lib/gcc/x86_64-linux-gnu/11 -L/usr/bin/../lib/gcc/x86_64-linux-gnu/11/../../../../lib64 -L/lib/x86_64-linux-gnu -L/lib/../lib64 -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib64 -L/usr/lib/llvm-14/bin/../lib -L/lib -L/usr/lib /tmp/hello-e13d0b.o -lgcc --as-needed -lgcc_s --no-as-needed -lc -lgcc --as-needed -lgcc_s --no-as-needed /usr/bin/../lib/gcc/x86_64-linux-gnu/11/crtendS.o /lib/x86_64-linux-gnu/crtn.o

 Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu 11.4.0-1ubuntu1~22.04' --with-bugurl=file:///usr/share/doc/gcc-11/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-11 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-bootstrap --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --enable-cet --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-11-XeT9lY/gcc-11-11.4.0/debian/tmp-gcn/usr --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu --with-build-config=bootstrap-lto-lean --enable-link-serialization=2
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 11.4.0 (Ubuntu 11.4.0-1ubuntu1~22.04)
COLLECT_GCC_OPTIONS='-v' '-o' 'out' '-mtune=generic' '-march=x86-64' '-dumpdir' 'out-'
 /usr/lib/gcc/x86_64-linux-gnu/11/cc1 -quiet -v -imultiarch x86_64-linux-gnu hello.c -quiet -dumpdir out- -dumpbase hello.c -dumpbase-ext .c "-mtune=generic" "-march=x86-64" -version -fasynchronous-unwind-tables -fstack-protector-strong -Wformat -Wformat-security -fstack-clash-protection -fcf-protection -o /tmp/ccPbHR8P.s
COLLECT_GCC_OPTIONS='-v' '-o' 'out' '-mtune=generic' '-march=x86-64' '-dumpdir' 'out-'
 as -v --64 -o /tmp/cccRglYa.o /tmp/ccPbHR8P.s
COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/11/:/usr/lib/gcc/x86_64-linux-gnu/11/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/11/:/usr/lib/gcc/x86_64-linux-gnu/
LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/11/:/usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/11/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/11/../../../:/lib/:/usr/lib/
COLLECT_GCC_OPTIONS='-v' '-o' 'out' '-mtune=generic' '-march=x86-64' '-dumpdir' 'out.'
 /usr/lib/gcc/x86_64-linux-gnu/11/collect2 -plugin /usr/lib/gcc/x86_64-linux-gnu/11/liblto_plugin.so "-plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/11/lto-wrapper" "-plugin-opt=-fresolution=/tmp/ccqOuxEe.res" "-plugin-opt=-pass-through=-lgcc" "-plugin-opt=-pass-through=-lgcc_s" "-plugin-opt=-pass-through=-lc" "-plugin-opt=-pass-through=-lgcc" "-plugin-opt=-pass-through=-lgcc_s" --build-id --eh-frame-hdr -m elf_x86_64 "--hash-style=gnu" --as-needed -dynamic-linker /lib64/ld-linux-x86-64.so.2 -pie -z now -z relro -o out /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/Scrt1.o /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/crti.o /usr/lib/gcc/x86_64-linux-gnu/11/crtbeginS.o -L/usr/lib/gcc/x86_64-linux-gnu/11 -L/usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu -L/usr/lib/gcc/x86_64-linux-gnu/11/../../../../lib -L/lib/x86_64-linux-gnu -L/lib/../lib -L/usr/lib/x86_64-linux-gnu -L/usr/lib/../lib -L/usr/lib/gcc/x86_64-linux-gnu/11/../../.. /tmp/cccRglYa.o -lgcc --push-state --as-needed -lgcc_s --pop-state -lc -lgcc --push-state --as-needed -lgcc_s --pop-state /usr/lib/gcc/x86_64-linux-gnu/11/crtendS.o /usr/lib/gcc/x86_64-linux-gnu/11/../../../x86_64-linux-gnu/crtn.o
COLLECT_GCC_OPTIONS='-v' '-o' 'out' '-mtune=generic' '-march=x86-64' '-dumpdir' 'out.'

See through the mess, we could summarize the steps into the following:

  1. The clang/gcc compiler driver calls itself with specific flags to invoke the compiler’s front end (includes the preprocessor stage.)
Written on March 5, 2024