Error using libusb library

Andrew23

I'm working to manage the USB communication between a Qt application and a PIC32 microcontroller device seen as a vendor class device. In the Microchip forum they suggested me to start from one application example written in Qt5 within their MLA library pakage. But now I'm trying to run the example but I get the following errorrs:

:-1: error: skipping incompatible C:\Microchip\mla\v2018_11_26\apps\usb\device\vendor_basic\utilities\libusb_cross_platform_example\src/libusb-1.0.lib when searching for -llibusb-1.0
:-1: error: skipping incompatible C:\Microchip\mla\v2018_11_26\apps\usb\device\vendor_basic\utilities\libusb_cross_platform_example\src/libusb-1.0.dll when searching for -llibusb-1.0
:-1: error: skipping incompatible C:\Microchip\mla\v2018_11_26\apps\usb\device\vendor_basic\utilities\libusb_cross_platform_example\src/libusb-1.0.lib when searching for -llibusb-1.0
:-1: error: skipping incompatible C:\Microchip\mla\v2018_11_26\apps\usb\device\vendor_basic\utilities\libusb_cross_platform_example\src/libusb-1.0.dll when searching for -llibusb-1.0
:-1: error: skipping incompatible C:\Microchip\mla\v2018_11_26\apps\usb\device\vendor_basic\utilities\libusb_cross_platform_example\src\libusb-1.0.lib when searching for -llibusb-1.0
:-1: error: cannot find -llibusb-1.0
:-1: error: collect2.exe: error: ld returned 1 exit status
:-1: error: [Makefile.Debug:78: windows/libusb_Demo.exe] Error 1

In the .pro file of the application I have

#-------------------------------------------------
#
# Project created by QtCreator 2012-06-06T13:21:53
#
#-------------------------------------------------

QT += core gui
QT += widgets


TARGET = libusb_Demo
TEMPLATE = app




SOURCES += main.cpp\
        mainwindow.cpp \
    usbcomm.cpp

HEADERS  += mainwindow.h \
    usbcomm.h

FORMS    += mainwindow.ui


#-------------------------------------------------
# Add LibUSB library
#-------------------------------------------------
LIBS += -L.\ -llibusb-1.0

#-------------------------------------------------
# Make sure to add the required libraries or
# frameoworks for the demo work depending on
# what OS is being used
#-------------------------------------------------
macx: LIBS += -framework CoreFoundation
win32: LIBS += -lSetupAPI

#-------------------------------------------------
# Make sure output directory for object file and
# executable is in the correct subdirectory
#-------------------------------------------------
macx {
    DESTDIR = mac
    OBJECTS_DIR = mac
    MOC_DIR = mac
    UI_DIR = mac
    RCC_DIR = mac
}
unix: !macx {
    DESTDIR = linux
    OBJECTS_DIR = linux
    MOC_DIR = linux
    UI_DIR = linux
    RCC_DIR = linux
}
win32 {
    DESTDIR = windows
    OBJECTS_DIR = windows
    MOC_DIR = windows
    UI_DIR = windows
    RCC_DIR = windows
}

OTHER_FILES +=

win32: LIBS += -L$$PWD/ -llibusb-1.0

INCLUDEPATH += $$PWD/
DEPENDPATH += $$PWD/

and in the README file I read

This is a cross platform project that is similar in functionality as the
"plug_and_play_example\src\vc++2008_express" project.  However, 
this version is developed in the Qt 5.x.x development environment (from www.qt.org), 
and uses the "libusb v1.0.x" APIs.

The libusb v1.0.x "driver" provides top level libusb API functions for accessing 
the USB device, but uses the Microsoft WinUSB driver when the application is 
used on the Windows platform.  Therefore, when this project is built and run 
on a Windows based machine, install and use the standard WinUSB driver package 
that comes with this demo, even when using this libusb application project.

The libusb-1.0.dll file and respective .lib file provided here are based on 
the libusb v1.0.19 source.  See www.libusb.org for details on the libusb APIs 
and links to the latest libusb source code and header download.

If using this project to build a Linux or Mac OS X executable, make sure
that the libusb v1.0.19 driver is available and installed correctly.

What's the problem here?

aha_1980

Hi @Andrew23,

which compiler are you using?
which architecture (32/64 bit?)

Regards

Andrew23

@aha_1980
compiler: MinGW 8.1.0 64-bit for C++
architecture: 64-bit

jsulm

@Andrew23 You should check whether this libusb-1.0 is also 64bit and which compiler was used to build it.

Andrew23

@jsulm Yes the problem was the 32-bit libusb library. I overwite it with the 64-bit version and it works. Thanks.

Now I'd like to know how to modify the project's settings to automatically choose the correct library. My .pro file is the following

#-------------------------------------------------
#
# Project created by QtCreator 2012-06-06T13:21:53
#
#-------------------------------------------------

QT += core gui
QT += widgets

TARGET = libusb_Demo
TEMPLATE = app

SOURCES += main.cpp\
        mainwindow.cpp \
    usbcomm.cpp

HEADERS  += mainwindow.h \
    usbcomm.h

FORMS    += mainwindow.ui

#-------------------------------------------------
# Add LibUSB library
#-------------------------------------------------
LIBS += -L.\ -llibusb-1.0

#-------------------------------------------------
# Make sure to add the required libraries or
# frameoworks for the demo work depending on
# what OS is being used
#-------------------------------------------------
macx: LIBS += -framework CoreFoundation
win32: LIBS += -lSetupAPI

#-------------------------------------------------
# Make sure output directory for object file and
# executable is in the correct subdirectory
#-------------------------------------------------
macx {
    DESTDIR = mac
    OBJECTS_DIR = mac
    MOC_DIR = mac
    UI_DIR = mac
    RCC_DIR = mac
}
unix: !macx {
    DESTDIR = linux
    OBJECTS_DIR = linux
    MOC_DIR = linux
    UI_DIR = linux
    RCC_DIR = linux
}
win32 {
    DESTDIR = windows
    OBJECTS_DIR = windows
    MOC_DIR = windows
    UI_DIR = windows
    RCC_DIR = windows
}

OTHER_FILES +=

win32: LIBS += -L$$PWD/ -llibusb-1.0

INCLUDEPATH += $$PWD/
DEPENDPATH += $$PWD/

Do you have any suggestion or documentation about the .pro file customization?

aha_1980

Hi @Andrew23,

I have the following in one of my projects:

*-msvc* {
  contains(QMAKE_TARGET.arch, x86_64) {
    # MSVC 64 bit
    LIBS += -L$$PWD/ni4882 -lni4882-64
  } else {
    # MSVC 64 bit
    LIBS += -L$$PWD/ni4882 -lni4882-32
  }
} else {
  # MinGW 32 bit
  LIBS += -L$$PWD/ni4882 -lgpib-32
}

By the way:

LIBS += -L.\ -llibusb-1.0

You are aware that there is already an entry win32: LIBS += -L$$PWD/ -llibusb-1.0 more below in your .pro file? $$PWD refers to the source directory during compilation, btw.

I hope that helps,

Regards