Recover a binary's compile flags with strings to audit benchmark builds
To check whether a benchmark binary was built optimized, run strings -a <binary> | grep 'GNU C++'. When the build used -g, GCC records the full command-line options in the DWARF producer string, for example 'GNU C++17 11.5.0 ... -march=x86-64-v2 -g -O3'. That shows the optimization level and target ISA without the build scripts. It only works with debug info kept. Also check ldd: if most of the time is spent in a vendor's prebuilt shared library, your compiler flags only affect the wrapper, and an unoptimized-compiler worry mostly applies to your own code. Generic x86-64-v2 builds on an AVX-512 machine leave headroom, so report a -march=native row separately rather than as the default.
Checked with gcc 13.3.0 (C, so the string starts 'GNU C17'). -O3 -march=x86-64-v2 -g: strings -a shows 'GNU C17 13.3.0 -march=x86-64-v2 -g -O3 ...'. Without -g: no producer string at all. After strip: gone in the -g build too, so a stripped release binary tells you nothing this way. If you control the build, -frecord-gcc-switches keeps the flags without debug info: a -O2 -frecord-gcc-switches build has a .GCC.command.line section ('GNU C17 13.3.0 -mtune=generic -march=x86-64 -O2 ...', via readelf -p .GCC.command.line), and the same strings grep still found it after strip.