Question

I’m trying to build OpenSSL with -Wa,–noexecstack, but can’t find anywhere in its config command-line to provide this flag. I’ve tried to set CFLAGS, but it appears to ignore that and just use its own.

This is an automated build working off a clean copy of the OpenSSL source, so a one-time hack of the config script isn’t really an option.

Is there a way to pass custom flags to OpenSSL’s build process?

Answer 1

The config script ignores CFLAGS, but not CC. So you can specify your compiler and give it the flags at the same time:

export CC="gcc -Wall -DHELLO_WORLD"; ./config

Alternatively, since config auto detects your platform and then runs Configure with preset compiler settings, you can add the compiler flags to your platform configuration. E.g., for my mac, I see this line when I first run config:

Operating system: i386-apple-darwinDarwin Kernel Version 10.8.0: Tue Jun 7 16:33:36 PDT 2011; root:xnu-1504.15.3~1/RELEASE_I386
Configuring for darwin-i386-cc

So if I open Configure, I can search for darwin-i386-cc and add the flags to the presets.

If you’re not using a preset configuration, then you’d just pass the flags directly to Configure on the command line and it’ll use them.