Cannot link library when compiling with gcc - c

Question

My directory structure is:
── bin
│   ├── mylib-osx.so.1.72
│   ├── mylib.so.1.72
├── my.c
I am trying to compile my.c and link mylib-osx.so.1.72 (I'm on a macOS), but to no avail:
ld: library not found for -l:PhotoDNAx64.so.1.72
I tried:
gcc -o my -lmylib-osx my.c
gcc -o my -lmylib-osx.so.1.72 my.c
gcc -o my -lmylib my.c
gcc -o my -L./bin -lmylib-osx my.c
gcc -o my -L./bin -l:"mylib-osx.so.1.72" my.c
What am I doing wrong and why cannot the library be found?

Answer 1

What am I doing wrong and why cannot the library be found?
Read about Invoking GCC. You was wrong in not reading that (or any other documentation of gcc).
Order of program arguments to gcc matters a lot (and in practice several arguments are very useful, e.g. both -Wall and -g at least, and probably -v sometimes). You want something like
gcc -v -Wall -g my.c -lmylib-osx -o my
(also try variants of that), since gcc is running some ld or equivalent linker command, and if you want to pass some -Llib-directory use something like
gcc -v -Wall -g my.c -L./bin -lmylib-osx -o my
and you also need to read the documentation of MacOSX linker (probably named ld). You could also read Levine's Linkers and loaders book.
If you are not happy with gcc (but please use a recent version, so GCC 8 in 2019, not the crappy software sold by Apple named gcc) consider using Clang (a recent version too, e.g. Clang 8 in 2019). It has the same limitation regarding order of program arguments than gcc does (since order of program arguments even mattered for Unix or POSIX cc).
In general, read the documentation of a command before asking questions here about that command. A minima, man gcc on your Apple (or Linux) computer.
PS. The last time I have used some MacOSX was in 2004. My biased recommendation is to install and use Linux (which I use since 1993; I tried MacOSX around 2004 during less than a year, and have been disappointed both by the operating system, including its display server and GUI desktop environment, and by the Apple hardware).