On 2021-05-12 18:26, Roberto Cornacchia wrote:
I was wondering,
-DCMAKE_BUILD_TYPE=Release (or RelWithDebInfo) doesn't seem to enable -O2 on gcc.
Is there a good reason for it or was it just forgotten?
Hi Roberto,
I usually configure like this (everything other than CMAKE_BUILD_TYPE should not matter for this issue): cd build/ cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=$(pwd)/install/ -GNinja -DCMAKE_EXPORT_COMPILE_COMMANDS=1 ../
If I then compile like this: VERBOSE=1 cmake --build .
I get the following: [...] [282/485] /usr/bin/cc -DLIBGDK -D_GNU_SOURCE -D_XOPEN_SOURCE -Dbat_EXPORTS -I../common/stream -I../common/utils -I../gdk -I. -I../common/options -Werror -Wall -Wextra -Werror-implicit-function-declaration -Wpointer-arith -Wundef -Wformat=2 -Wformat-overflow=1 -Wno-format-truncation -Wno-format-nonliteral -Wno-cast-function-type -Winit-self -Winvalid-pch -Wmissing-declarations -Wmissing-format-attribute -Wmissing-prototypes -Wno-missing-field-initializers -Wold-style-definition -Wpacked -Wunknown-pragmas -Wvariadic-macros -Wstack-protector -fstack-protector-all -Wpacked-bitfield-compat -Wsync-nand -Wjump-misses-init -Wmissing-include-dirs -Wlogical-op -Wduplicated-cond -Wduplicated-branches -Wrestrict -Wnested-externs -Wmissing-noreturn -Wuninitialized -Wno-char-subscripts -Wunreachable-code -O3 -DNDEBUG -fPIC -std=gnu99 -MD -MT gdk/CMakeFiles/bat.dir/gdk_analytic_func.c.o -MF gdk/CMakeFiles/bat.dir/gdk_analytic_func.c.o.d -o gdk/CMakeFiles/bat.dir/gdk_analytic_func.c.o -c ../gdk/gdk_analytic_func.c [...] which includes the -O3 optimization flag. This is on default branch, but I am pretty sure it works similarly in all branches. If you have configured the build directory for a debug build type previously (cmake -DCMAKE_BUILD_TYPE=Debug) this might be the reason why it is not working. Try a new directory with a fresh cmake execution.
Best regards, Panos.