./configure does not check libpng correctly in recent cygwin. (cvs source 2010-08-14)

[Tatsuro M. <tma...@ya...>]

Hello

I have found that during in the 'make pdffigures'.

../src/gnuplot plotstyles.gnu
"plotstyles.gnu", line 327: This copy of gnuplot cannot read png/gif/jpeg images

make: *** [figures] Error 1

I have checked config.h and config.log.

I found in config.h

/* Define if libgd supports png. */
/* #undef HAVE_GD_PNG */

and found in config.log

configure:8811: checking for gdImageStringFT in -lgd
configure:8836: gcc -shared-libgcc -o conftest.exe -O3 -fomit-frame-pointer   -I/usr/local/include 
-L/usr/lib conftest.c -lgd   -lXpm -lX11 -ljpeg -lfontconfig -lfreetype -lpng12 -lz -liconv -ljpeg
-lfreetype >&5
configure:8836: $? = 0
configure:8845: result: yes
configure:8904: checking for gdImagePng in -lgd
configure:8929: gcc -shared-libgcc -o conftest.exe -O3 -fomit-frame-pointer   -I/usr/local/include 
-L/usr/lib conftest.c -lgd   -lXpm -lX11 -ljpeg -lfontconfig -lfreetype -lpng12 -lz -liconv -ljpeg
-lfreetype -lpng >&5
/usr/lib/gcc/i686-pc-cygwin/4.3.4/../../../../i686-pc-cygwin/bin/ld: cannot find -lpng
collect2: ld returned 1 exit status
configure:8929: $? = 1

Now in the latest cygwin, libpng is removed and only libpng12 exist.
Perhaps the second test effective and png was not effective thus  resulted in 

/* Define if libgd supports png. */
/* #undef HAVE_GD_PNG */

in config.h.

If the first check is OK and then second check should be skipped.

Temporally I have made a symbolic link to avoid the detection failure of the libpng.  
 ln -s libpng12.dll.a libpng.dll.a

Regards

Tatsuro


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