CMake config generates invalid compiler flag when the (optional) dependency libusb-1.0 can not be found

[harendt]

When I'm compiling code that depends on PCL without the (optional) dependency libusb-1.0, I get a huge number of the following warnings:

:0:15: warning: ISO C99 requires whitespace after the macro name [enabled by default]

The warning comes from the token -DDISABLE_LIBUSB-1.0 that is added to the compiler flags by PCL. The minus sign and the dot in DISABLE_LIBUSB-1.0 are not allowed for macro names.

I found the place where this invalid macro definition comes from (PCLConfig.cmake.in, line 618):

add_definitions("-DDISABLE_${LIB}")

When ${LIB} is LIBUSB-1.0, it should be changed to LIBUSB_1_0 or something similar.

[SergioRAgostinho]

Can you provide more information on your setup? I just tried disabling libusb and building and no warnings were generated.

[harendt]

I'm working on Ubuntu 14.04. And libusb is not installed. I compiled PCL (version 1.7.2) on my own. The error occurs, when I try to compile code, that depends on PCL (pcl-common and pcl-io, I guess). I'm using CMake as build system. And CMake's function find_package() uses the file PCLConfig.cmake that is installed by PCL.

On line 618 this CMake file adds the compiler flag -DDISABLE_LIBUSB-1.0, if libusb is not found:

add_definitions("-DDISABLE_${LIB}")

The problem is that -- as the warning indicates -- the characters - and . are not allowed in macro definitions. Hence these characters should be replaced (e.g. replaced by _).

I could add a patch to PCLConfig.cmake, that replaces these invalid characters, but I don't know, if this would affect anything else.

[taketwo]

I don't see any usage of such DISABLE variables anywhere besides pcl_config.h.in, where OpenNI and QHull support is tested. I think it's very safe to fix the invalid characters in -DDISABLE_LIBUSB-1.0. I'd even say it's okay to remove it completely, but we don't need to go that far :)