mjhjmtu

While installing the cudnn library, I came across this in the INSTALL.txt file:

Add [installpath] to your build and link process by adding
-I[installpath] to your compile
line and -L[installpath] -lcudnn to your link line.

What does compile and link line mean? Do I do this, while compiling myFile.c which uses cudnn:

gcc myFile.c -L /path/to/library -l /name/of/library

Or something else?

PS: They have also mentioned to do this:

cd <installpath>
export LD_LIBRARY_PATH=`pwd`:$LD_LIBRARY_PATH

But won't I need to write this out to my .bashrc file so that the environment variable is set every time my machine runs?

Your gcc command combines the compile and link phase, so you need to add all the options given:

gcc -Iincludepath myFile.c -Llibpath -lcudnn

replacing includepath and libpath as appropriate.

And yes, you’ll probably want to edit your .bashrc to set LD_LIBRARY_PATH:

export LD_LIBRARY_PATH=libpath:$LD_LIBRARY_PATH

replacing libpath as appropriate.

includepath needs to point to the headers (.h files), libpath to the library (.so).

Compiling and linking are the 2 major steps in the creation of an executable. Both can be done with the gcc command. There is also a preprocessing step (before compilation) and an assembly (after compilation); these are almost always done at the same time as compiling so the combination "preprocess then compile then assemble" are treated as a single step called "compiling" for short.

The steps performed by a particular gcc command line can be determined as follows:

Write down the order "preprocess, compile, assemble, link".

If the input file is named *.i, remove the preprocess step (.i files are already preprocessed).

If the input file is named *.s, remove the preprocess and compile steps (.s files are already compiled).

If the input file is named *.o, remove the preprocess, compile, and assemble steps (.o files are assembled).

If there's a -x option, use it instead of the name of the input file in the preceding steps. (This is rare)

If the -c option is used, remove the link step.

If the -S option is used, remove the assemble and link steps.

If the -E option is used, remove the compile, assemble, and link steps.

In summary, the type of the input file determines where you start in the preprocess-compile-assemble-link sequence, and the -c/-S/-E options determine where you stop (they request output files of type *.o, *.s, and *.i respectively - although -E actually outputs to stdout by default).

Your command line has none of the output-type options, and its input file is named *.c, so it is a compile line and a link line. This is a normal way to compile small programs. With larger programs, you usually don't want to compile everything all at once. It's better to save the intermediate *.o files for reuse and only recompile them when their source file changes.

The "recompile as needed" development cycle involves gcc -c commands to create the *.o files, usually one at a time, and a gcc *.o -o theprogram command to do the linking. These commands are commonly found in a Makefile and are referred to as "compile lines" and "link lines".