Ubuntu18.04 + ROS melodic 安装google-cartographer，

Compiling Cartographer ROS — Cartographer ROS documentation

出现下面的报错，

$ catkin_make_isolated --install --use-ninja

...

CMake Error at /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfig.cmake:27 (message):
  The imported target "Qt5::Gui" references the file

     "/usr/lib/x86_64-linux-gnu/libEGL.so"

  but this file does not exist.  Possible reasons include:

  * The file was deleted, renamed, or moved to another location.

  * An install or uninstall procedure did not complete successfully.

  * The installation package was faulty and contained

     "/usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfigExtras.cmake"

  but not all the files it references.

Call Stack (most recent call first):
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfigExtras.cmake:50 (_qt5_Gui_check_file_exists)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfigExtras.cmake:72 (_qt5gui_find_extra_libs)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfig.cmake:184 (include)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Widgets/Qt5WidgetsConfig.cmake:101 (find_package)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5/Qt5Config.cmake:28 (find_package)
  CMakeLists.txt:56 (find_package)


-- Configuring incomplete, errors occurred!
See also ...

解决办法：

先查看一下libegl到底怎么回事

~/projects/cartographer$ ls /usr/lib/x86_64-linux-gnu | grep -i libegl
libEGL_mesa.so.0
libEGL_mesa.so.0.0.0
libEGL_nvidia.so.0
libEGL_nvidia.so.470.82.01
libEGL.so
libEGL.so.1
libEGL.so.1.1.0

然后查检一下这个libEGL.so为什么找不到

~/projects/cartographer$ ls -l /usr/lib/x86_64-linux-gnu/libEGL.so
lrwxrwxrwx 1 root root 15 5月  10  2019 /usr/lib/x86_64-linux-gnu/libEGL.so -> libEGL.so.1.0.0

~/projects/cartographer$ ls -l /usr/lib/x86_64-linux-gnu/libEGL.so.1
lrwxrwxrwx 1 root root 15 2月  22 08:34 /usr/lib/x86_64-linux-gnu/libEGL.so.1 -> libEGL.so.1.1.0

这样，发现libEGL.so链接的是libEGL.so.1.0.0，而实际这里只有libEGL.so.1.1.0，不存在libEGL.so.1.0.0；当然你也可以找到libEGL.so这个文件，右击属性就会发现这个文件显示的是

链接(已断) (inode/symlink)，或Link (broken) (inode/symlink)

原因就是链接已经断掉了，我们把它重新链接上（顺便再检查一下）就好了，

~/projects/cartographer$ sudo ln -sf /usr/lib/x86_64-linux-gnu/libEGL.so.1.1.0  /usr/lib/x86_64-linux-gnu/libEGL.so

~/projects/cartographer$ ls -l /usr/lib/x86_64-linux-gnu/libEGL.so
lrwxrwxrwx 1 root root 41 2月  27 15:37 /usr/lib/x86_64-linux-gnu/libEGL.so -> /usr/lib/x86_64-linux-gnu/libEGL.so.1.1.0

当然，为了避免弄错，你也可以先备份后再进行上速的强行替换操作。

先备份再
sudo rm /usr/lib/x86_64-linux-gnu/libEGL.so
然后再
sudo ln -sf /usr/lib/x86_64-linux-gnu/libEGL.so.1.1.0  /usr/lib/x86_64-linux-gnu/libEGL.so

--------------------------------------------

对于出现的另一个同样的报错，

...
CMake Error at /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfig.cmake:27 (message):
  The imported target "Qt5::Gui" references the file

     "/usr/lib/x86_64-linux-gnu/libGL.so"

  but this file does not exist.  Possible reasons include:

  * The file was deleted, renamed, or moved to another location.

  * An install or uninstall procedure did not complete successfully.

  * The installation package was faulty and contained

     "/usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfigExtras.cmake"

  but not all the files it references.

Call Stack (most recent call first):
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfigExtras.cmake:50 (_qt5_Gui_check_file_exists)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfigExtras.cmake:74 (_qt5gui_find_extra_libs)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Gui/Qt5GuiConfig.cmake:184 (include)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5Widgets/Qt5WidgetsConfig.cmake:101 (find_package)
  /usr/lib/x86_64-linux-gnu/cmake/Qt5/Qt5Config.cmake:28 (find_package)
  CMakeLists.txt:56 (find_package)


-- Configuring incomplete, errors occurred!
See also ...

采取类似的手段就可以了，

~/projects/cartographer$ ls /usr/lib/x86_64-linux-gnu | grep -i libgl
libgl2ps.so
libgl2ps.so.1.4
libgl2ps.so.1.4.0
libglade
libglade-2.0.so.0
libglade-2.0.so.0.0.7
libglapi.so.0
libglapi.so.0.0.0
libGLdispatch.so
libGLdispatch.so.0
libGLESv1_CM_nvidia.so.1
libGLESv1_CM_nvidia.so.470.82.01
libGLESv1_CM.so
libGLESv1_CM.so.1
libGLESv1_CM.so.1.0.0
libGLESv1_CM.so.1.2.0
libGLESv2_nvidia.so.2
libGLESv2_nvidia.so.470.82.01
libGLESv2.so
libGLESv2.so.2
libGLESv2.so.2.1.0
libglib-2.0.a
libglib-2.0.so
libglib-2.0.so.0
libglib-2.0.so.0.5600.4
libglog.a
libglog.so
libglog.so.0
libglog.so.0.0.0
libGL.so
libGL.so.1
libGL.so.1.7.0
libGLU.a
libGLU.so
libGLU.so.1
libGLU.so.1.3.1
libglut.a
libglut.so
libglut.so.3
libglut.so.3.9.0
libGLX_indirect.so.0
libGLX_mesa.so.0
libGLX_mesa.so.0.0.0
libGLX_nvidia.so.0
libGLX_nvidia.so.470.82.01
libGLX.so
libGLX.so.0

然后，

~/projects/cartographer$ ls -l /usr/lib/x86_64-linux-gnu/libGL.so
lrwxrwxrwx 1 root root 14 5月  10  2019 /usr/lib/x86_64-linux-gnu/libGL.so -> libGL.so.1.0.0

~/projects/cartographer$ sudo ln -sf /usr/lib/x86_64-linux-gnu/libGL.so.1.7.0  /usr/lib/x86_64-linux-gnu/libGL.so

~/projects/cartographer$ ls -l /usr/lib/x86_64-linux-gnu/libGL.so
lrwxrwxrwx 1 root root 40 2月  27 15:40 /usr/lib/x86_64-linux-gnu/libGL.so -> /usr/lib/x86_64-linux-gnu/libGL.so.1.7.0

本文结束。