Posts tagged "from source to process"

With gdb I followed what calls main, where constructors are called from, and in which order init_array and fini_array run. A program without libc starts in 56 microseconds instead of 143, and Rust std has its own function in init_array.

I wrote a small library that counts malloc calls and preloaded it into C, Rust and ls. The famous dlsym trap did not appear with glibc 2.43, but ls hid my output in a way I did not expect, and the static binary ignored the library completely.

I watched one GOT slot in gdb before and after the first call to puts, measured what lazy binding costs on that first call, and compared it with -z now, LD_BIND_NOW, -fno-plt and a Rust binary that never uses the PLT for libc.

I built a small shared library and a program that needs it, got the famous cannot open shared object file, and fixed it three ways while LD_DEBUG=libs showed every directory the loader tried, including why RPATH and RUNPATH give different answers.

I built the same programs static and dynamic, in C and Rust, and compared files, system calls, start time and shared memory. Static starts twice as fast here, but a static program that looks up an unknown user loaded the shared libc anyway and crashed.