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. 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
