Ubuntu installation Dlib appears dlib.so:undefined SYMBOL:PNG_SET_LONGJMP_FN

Refer to the online tutorial installation Dlib

sudo apt-get install libboost-python-dev cmakesudo pip install dlib

Installation Tutorial 2

Go to the official website to download the installation package, unzip

Tools required to install the compilation

sudo apt-get install CMake
sudo apt-get install Libboost-python-dev

Go to Dlib's directory sudo python setup.py install

the following error occurred
$ Pythonpython2.7.12 (default, Nov 19 2016, 06:48:10) [GCC5.4.0 20160609] on Linux2type" Help","Copyright","credits" or "License"  forMore information.>>>ImportDlibtraceback (most recent): File"<stdin>", Line 1,inch<module>importerror:./dlib.so:undefined SYMBOL:PNG_SET_LONGJMP_FN>>>

Cause of the problem

This is the time to compile the project on Linux, a dynamic library layer used by a function implementation is not found,

The system installed libpng16.so.16.29.0*, readelf-s the next file, there is png_set_longjmp_fn this symbol

lrwxrwxrwx  1 root root         19 June   1 10:49 libpng16.so libpng16.so.16.29.0*lrwxrwxrwx  1 root Root         19 June   1 10:49 libpng16.so.16-libpng16.so.16.29.0*-rwxr-xr-x  1 root root     926416 June   1 10:49 libpng16.so.16.29.0*

Find cause Discovery:

There is also a location in the system where the old version of Libpng12 is installed,

/lib/x86_64-linux-gnu

-rwxrwxrwx 1 root root 149800 October 19:21 libpng12.so.0*-rwxrwxrwx 1 root root 149800 October 19:21 libpng12.so.0.54.0*

In this version of the libpng is not png_set_longjmp_fn function definition, compile the relevant library dlib dependent on the time,

The first is the link to/lib/x86_64-linux-gnu/libpng12.so.0 cannot find the function, error.

Workaround 1: (recommended)

Cd/lib/x86_64-linux-gnu

sudo rm libpng12.so.0 (delete old version of Libpng library here)

sudo rm libpng12.so.0.54.0

sudo ln-s/usr/local/lib/libpng16.so.16./libpng16.so.16 (Establish a link to libpng16)

When the system compiles, it links to/usr/local/lib/libpng16.so.16 's library

Workaround 2:

PNG Usage Process issues Summary:

(1) libpng "PNG_SET_LONGJMP_FN" not found

Solution Ideas

in my case, I has the old PNG 1.2 came with my Ubuntu installed IN/USR. I installed the 1.6.x in/usr/local. In my make system, the default Include/usr/include and Linking/usr/lib were picked up. When compiling any software this rely on the new interface, you need to add

cppflags= "-i/usr/local/include $CPPFLAGS"
ldflags= "-l/usr/local/lib $LDFLAGS"

This'll pick up

grep png_set_longjmp_fn png.h
Png_export (8, jmp_buf*, PNG_SET_LONGJMP_FN, Png_structrp png_ptr,
(*PNG_SET_LONGJMP_FN (png_ptr), longjmp, (sizeof (JMP_BUF) )))

when compiling the program, add it to the makefile .

cppflags= "-i/usr/local/include $CPPFLAGS"
ldflags= "-l/usr/local/lib $LDFLAGS"
make the dependent libpng library point to the latest LIBPNG16 you have installed

Ubuntu installation Dlib appears dlib.so:undefined SYMBOL:PNG_SET_LONGJMP_FN