Bashing Windows

 1 min read

I seem to blog the most about needing to blog more often. Unfortunately for me, interesting things don’t happen often. So instead of waiting for something cool to happen, I’m just going to blog about the little things and hope for the best.

I drafted a post about my adventures with trying to compile some open source software, but it turned out far too long and it didn’t actually concentrate on the point I was trying to make. So instead I’ll jump right to it.

Yesterday I decided, randomly, to have a look at libcurl. It’s a surprisingly powerful library for C that supports a huge amount of internet protocols with only a few function calls. The code examples on the website made it look easy enough to use, so I thought I’d download it and see what I can do with it. Unfortunately compiling it myself turned out to be annoyingly difficult, so I just downloaded the binaries. Naturally these were all in MinGW form and I needed them them to be MSVC compatible.

After some googling I found that MinGW comes with a tool called pexports which dumps all the symbols of a DLL. So using that I wrote a Bash script that does this for all the DLLs in a directory:

for i in $( ls | grep ".*\.dll" | sed "s/.dll//" ); do
    pexports "$i.dll" > "$i.def"
    echo "lib /machine:i386 /def:$i.def" >> makelib.bat

This creates a .def file for each DLL which lists all the symbols that must be exported and adds a line to makelib.bat which will create the MSVC import library. The two pronged approach is unfortunately necessary here because the Microsoft LIB tool won’t run through the Cygwin prompt.

The first line might seem complicated, but it’s not too bad. ls lists all the files in the current directory, grep then singles out all the .dll files, and finally sed removes the trailing .dll. In the loop itself $i will therefore always be of the form <mydll> instead of <mydll>.dll.

I’m no expert with Bash scripting so there’s probably an easier way to do it.