On Tue, Apr 20, 2021 at 11:21 PM Tadeus Prastowo <tadeus.prastowo@xxxxxxxx> wrote: > > On Wed, Apr 21, 2021 at 1:29 AM Peng Yu <pengyu.ut@xxxxxxxxx> wrote: > > I tried with hola.s below. > > > > https://cs.lmu.edu/~ray/notes/gasexamples/ > > > > It seems that gcc -v -Wl,-v gives quite complex underlying commands. > > But most of the options are not useful. > > > > The minimal commands should be just the following (on Linux). Why are > > there so many irrelevant command line options passed down to ld? > > If in addition to -v -Wl,-v you pass the compiler option -fno-lto, the > options pertaining to LTO (link-time optimization) will not appear. Since it is *link*-time optimization, I suppose it is ld who does the actual work? So for compiling a .c file, the real work of the gcc package that is rather significant is just done by cc1. All the rest work is dispatched to as and ld, which could have been implemented in bash or some shell language instead of C. If it were implemented in a shell language, it would be easier to see what is going on below the surface, instead of relying on the -v option. (Probably it is easier to maintain shell scripts rather than C code? Also, just for calling others programs, it seems shell is a better implementation language than C.) > So, you are left with the following parameters given to `/usr/bin/ld', > which is the static linker provided by the GNU Binutils project, > quoting your e-mail: > > > --build-id > > Not needed but may ease debugging [1]. > > > --eh-frame-hdr > > Not needed [1] but required by some debugging standard [2]. > > > -m elf_x86_64 > > --hash-style=gnu > > Not needed because ld is built with some default [1]. > > > --as-needed > > Not needed but may save some space [1]. > > > -dynamic-linker /lib64/ld-linux-x86-64.so.2 > > The dynamic linker, which is provided by the GNU C Library project. > > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crt1.o > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crti.o > > /usr/lib/gcc/x86_64-linux-gnu/10/crtbegin.o > > The C runtime, which is run to initialize the C library and then to > invoke the main function. They are provided by the GNU C Library > project. > > > -L/usr/lib/gcc/x86_64-linux-gnu/10 > > -L/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu > > -L/usr/lib/gcc/x86_64-linux-gnu/10/../../../../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/10/../../.. > > Those are all paths where ld can additionally search for any library > mentioned down the line (e.g., -lgcc). They are not needed if the > default search paths suffice [1]. > > > -v > > Not needed [1]. > > > /tmp/mktemp/ccETAQ7Y.o > > The object file to link. > > > -lgcc > > Not needed unless the object file needs something from libgcc. > > > --push-state > > --as-needed > > -lgcc_s > > --pop-state > > Not needed unless the object file needs something from libgcc_s. > > > -lc > > The C library. > > > -lgcc > > Either spurious repetition or repeated just in case libgcc_s needs > something from libgcc. > > > --push-state > > --as-needed > > -lgcc_s > > --pop-state > > Either spurious repetition or repeated just in case libgcc needs > something from libgcc_s. > > > /usr/lib/gcc/x86_64-linux-gnu/10/crtend.o > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crtn.o > > The C runtime, which is run to terminate the C library after returning > from the main function. They are provided by the GNU C Library > project. > > [1] https://sourceware.org/binutils/docs/ld/Options.html > [2] https://stackoverflow.com/a/26302715 > > > What > > do crt1.o, crti.o and crtn.o do in details? Thanks. > > You should ask in the GNU C Library help mailing list [3]. Or, just > see the source code, for example, the comment at the start of [4], > which refers to [5]. > > [3] https://sourceware.org/mailman/listinfo/libc-help/ > [4] https://sourceware.org/git/?p=glibc.git;a=blob;f=csu/Makefile;h=3054329cea4a276d5e2312e6b5d659192ff06423;hb=HEAD > [5] https://sourceware.org/git/?p=glibc.git;a=tree;f=elf;h=6063f27163949ad249e899fc1aa8c542c9a08ed3;hb=HEAD > > > tmpfile=$(mktemp -u) > > as -o "$tmpfile" hola.s > > cmd=( > > ld > > -dynamic-linker /lib64/ld-linux-x86-64.so.2 > > /usr/lib/x86_64-linux-gnu/crt1.o > > /usr/lib/x86_64-linux-gnu/crti.o > > /usr/lib/x86_64-linux-gnu/crtn.o > > -lc > > "$tmpfile" > > ) > > "${cmd[@]}" > > > > > > $ gcc -Wl,-v -v -no-pie hola.s > > Using built-in specs. > > COLLECT_GCC=gcc > > COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper > > OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa:hsa > > OFFLOAD_TARGET_DEFAULT=1 > > Target: x86_64-linux-gnu > > Configured with: ../src/configure -v --with-pkgversion='Debian > > 10.2.1-6' --with-bugurl=file:///usr/share/doc/gcc-10/README.Bugs > > --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 > > --prefix=/usr --with-gcc-major-version-only --program-suffix=-10 > > --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 --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-10-Km9U7s/gcc-10-10.2.1/debian/tmp-nvptx/usr,amdgcn-amdhsa=/build/gcc-10-Km9U7s/gcc-10-10.2.1/debian/tmp-gcn/usr,hsa > > --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-mutex > > Thread model: posix > > Supported LTO compression algorithms: zlib zstd > > gcc version 10.2.1 20210110 (Debian 10.2.1-6) > > COLLECT_GCC_OPTIONS='-v' '-no-pie' '-mtune=generic' '-march=x86-64' > > as -v --64 -o /tmp/mktemp/ccETAQ7Y.o hola.s > > GNU assembler version 2.35.2 (x86_64-linux-gnu) using BFD version (GNU > > Binutils for Debian) 2.35.2 > > COMPILER_PATH=/usr/lib/gcc/x86_64-linux-gnu/10/:/usr/lib/gcc/x86_64-linux-gnu/10/:/usr/lib/gcc/x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/10/:/usr/lib/gcc/x86_64-linux-gnu/ > > LIBRARY_PATH=/usr/lib/gcc/x86_64-linux-gnu/10/:/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/:/usr/lib/gcc/x86_64-linux-gnu/10/../../../../lib/:/lib/x86_64-linux-gnu/:/lib/../lib/:/usr/lib/x86_64-linux-gnu/:/usr/lib/../lib/:/usr/lib/gcc/x86_64-linux-gnu/10/../../../:/lib/:/usr/lib/ > > COLLECT_GCC_OPTIONS='-v' '-no-pie' '-mtune=generic' '-march=x86-64' > > /usr/lib/gcc/x86_64-linux-gnu/10/collect2 -plugin > > /usr/lib/gcc/x86_64-linux-gnu/10/liblto_plugin.so > > -plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper > > -plugin-opt=-fresolution=/tmp/mktemp/ccBVaooZ.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 > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crt1.o > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crti.o > > /usr/lib/gcc/x86_64-linux-gnu/10/crtbegin.o > > -L/usr/lib/gcc/x86_64-linux-gnu/10 > > -L/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu > > -L/usr/lib/gcc/x86_64-linux-gnu/10/../../../../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/10/../../.. -v > > /tmp/mktemp/ccETAQ7Y.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/10/crtend.o > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crtn.o > > collect2 version 10.2.1 20210110 > > /usr/bin/ld -plugin /usr/lib/gcc/x86_64-linux-gnu/10/liblto_plugin.so > > -plugin-opt=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper > > -plugin-opt=-fresolution=/tmp/mktemp/ccBVaooZ.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 > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crt1.o > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crti.o > > /usr/lib/gcc/x86_64-linux-gnu/10/crtbegin.o > > -L/usr/lib/gcc/x86_64-linux-gnu/10 > > -L/usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu > > -L/usr/lib/gcc/x86_64-linux-gnu/10/../../../../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/10/../../.. -v > > /tmp/mktemp/ccETAQ7Y.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/10/crtend.o > > /usr/lib/gcc/x86_64-linux-gnu/10/../../../x86_64-linux-gnu/crtn.o > > GNU ld (GNU Binutils for Debian) 2.35.2 > > COLLECT_GCC_OPTIONS='-v' '-no-pie' '-mtune=generic' '-march=x86-64' > > > > -- > > Regards, > > Peng > > -- > Best regards, > Tadeus -- Regards, Peng
