Is PKG_CONFIG_PATH being ignored by pkg-config in some circumstances?

[Michael Gooch]

either that or it is not capable of handling the ':' separated list in 
PKG_CONFIG_PATH that the manual file says it is.

I am using modules http://modules.sourceforge.net/

I cannot load all the modules' *.pc files into the same directory, 
because conflicting files may exist in different builds. I REQUIRE that 
the pkg-config utilities work as described by searching all the paths 
listed in PKG_CONFIG_PATH and not expecting only a single path there, or 
all files in a central location.

do I need to enable that behavior by adding a configure flag to the 
pkg-config build process?

what do I do?

for instance I am trying to compile R and have it link against cairo, 
but pkg-config is telling R that i doesn't know anything about cairo, 
despite it being installed at 
/UCHC/HPC/Gooch/biotoolmodules/cairo/1.14.2, having the /lib/pkgconfig 
directory with the required files, and having that path added to 
PKG_CONFIG_PATH

the current value of PKG_CONFIG_PATH is : 
/UCHC/HPC/Gooch/biotoolmodules/curl/7.42.1/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/openssl/1.0.2a/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/libmetalink/0.1.2/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/libIDN/1.30/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/glib2/2.44.0/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/pixman/0.32.6/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/libsigc++/2.4.1/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/cairo/1.14.2/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/libffi/3.2.1/lib/pkgconfig:/UCHC/HPC/Gooch/biotoolmodules/gcc/5.1.0/lib64/pkgconfig


the contents of the manfile says:
PKG_CONFIG_PATH
               A  colon-separated  (on  Windows, semicolon-separated) 
list of directories to search for .pc files. The default directory will 
always be searched after searching the
               path; the default is libdir/pkgconfig:datadir/pkgconfig 
where libdir is the libdir for pkg-config and datadir is the datadir for 
pkg-config when it was installed.

so i'm not sure what is going wrong. sometimes pkg-config --list-all 
shows me all the packages, other times i get no return text at all.