[Guy Harris <guy@xxxxxxxxxxxx>]

On Apr 20, 2018, at 1:35 PM, Guy Harris <guy@xxxxxxxxxxxx> wrote:

> From a quick look at the definition of pkg_search_module in CMake 3.5.1, it does *NOT* check for -isystem in the output of pkg-config --cflags, it only checks for -I and --cflags-only-I.

No, --cflags-only-I is what's used as an argument to pkg-config to get the -I arguments.  It *doesn't* provide -isystem arguments; you need either --cflags *or --cflags-only-other.

> So perhaps what we have to do with *any* package found with pkg-config is to use *all* of <XPREFIX>_CFLAGS, rather than using <XPREFIX>_INCLUDE_DIRS.  There might be other flags that pig-config supplies that might be necessary when compiling - presumably it wouldn't supply them if they weren't necessary or at least recommended.

Or add <XPREFIX>_CFLAGS_OTHER, in addition to using <XPREFIX>_INCLUDE_DIRS, which might be a bit safer (and simpler).