#73 Makefile-nolib fails linking with missing libpng symbols

[Hanspeter Niederstrasser]

gcc  -o pngcrush pngcrush.o -L/sw/lib -L/usr/lib -lpng -lz -lm
Undefined symbols for architecture x86_64:
  "_png_crc_finish", referenced from:
      _pngcrush_measure_idat in pngcrush.o
  "_png_crc_read", referenced from:
      _pngcrush_measure_idat in pngcrush.o
  "_png_read_transform_info", referenced from:
      _main in pngcrush.o
  "_png_reset_crc", referenced from:
      _pngcrush_measure_idat in pngcrush.o
ld: symbol(s) not found for architecture x86_64

When linking pngcrush, the above symbols are not found. libpng16.dylib is in /sw/lib, and those four symbols are marked as local (non-external) in the library.

Building pngcrush with the bundled zlib and libpng libraries works.

[Glenn Randers-Pehrson]

What version of pngcrush are you trying to build?

[Hanspeter Niederstrasser]

v1.8.7 using the pngcrush-1.8.7.tar.gz tarball and make -f Makefile-nolib PNGINC=/sw/include PNGLIB=/sw/lib, but the undefined symbols error also happens with git HEAD.

[Glenn Randers-Pehrson]

Please try git HEAD (version 1.8.8)

[Hanspeter Niederstrasser]

Same error after updating to commit a828b8ea07 (current HEAD) in git:

gcc  -o pngcrush pngcrush.o -L/sw/lib -lpng -lz -lm
Undefined symbols for architecture x86_64:
  "_png_crc_finish", referenced from:
      _pngcrush_measure_idat in pngcrush.o
  "_png_crc_read", referenced from:
      _pngcrush_measure_idat in pngcrush.o
  "_png_read_transform_info", referenced from:
      _main in pngcrush.o
  "_png_reset_crc", referenced from:
      _pngcrush_measure_idat in pngcrush.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[Glenn Randers-Pehrson]

Make sure you don't have png.h in the directory where you are trying to build the nolib version. You should only have

cexcept.h  ChangeLog.html  LICENSE  Makefile  Makefile.solaris  pngcrush.c

If you are in a directory that contains the libpng and zlib sources, you can build a "nolib"
version by moving png.h out of the way:

mv png.h png.h_embedded
make clean
make -f Makefile-nolib

[Glenn Randers-Pehrson]

Try the GIT HEAD again. I revised Makefile-nolib to temporarily move png.h out of the way,
so you don't have to do it manually as I suggested in the previous comment. Just do

make -f Makefile-nolib ...

as before.

[Hanspeter Niederstrasser]

The mv png.h commands in Makefile-nolib allowed linking to finish successfully. But it led me try to figure out why internal-png.h was being found because I thought I was making sure that system -Iincludes came before local -Iincludes. The following patch also finishes linking, and there's no need to move files around:

diff --git a/Makefile-nolib b/Makefile-nolib
index 79e12a9..fcb9ce9 100644
--- a/Makefile-nolib
+++ b/Makefile-nolib
@@ -21,7 +21,7 @@ CC = gcc
 LD = gcc
 RM = rm -f

-CPPFLAGS = -I $(PNGINC)
+CPPFLAGS = -I$(PNGINC)

 CFLAGS = -g -O3 -fomit-frame-pointer -Wall
 # [note that -Wall is a gcc-specific compilation flag ("all warnings on")]
@@ -48,10 +48,7 @@ EXES = $(PNGCRUSH)$(E)
 all:  $(EXES)

 pngcrush$(O): pngcrush.c cexcept.h
-   touch png.h
-   mv png.h png.h_embedded
    $(CC) -c $(CPPFLAGS) $(CFLAGS) $<
-   mv png.h_embedded png.h

 $(PNGCRUSH)$(E): $(OBJS)
    $(LD) $(LDFLAGS) -o $@ $(OBJS) $(LIBS)
diff --git a/pngcrush.c b/pngcrush.c
index 904ea70..5c7e355 100644
--- a/pngcrush.c
+++ b/pngcrush.c
@@ -336,8 +336,7 @@ Change log:

 Version 1.8.8 (built with libpng-1.6.26beta01 and zlib-1.2.8)
   Fixed "nolib" build (bug report by Hanspeter Niederstrasser).
-    Moves png.h temporarily to png.h_embedded, then puts it back after
-    compiling pngcrush.c.
+    Make sure we use system-png.h, and not the local file.

 Version 1.8.7 (built with libpng-1.6.25 and zlib-1.2.8)
   Do not check the ADLER32 CRC while reading except during the final write
@@ -1451,7 +1450,7 @@ static int verbose = 1;
 #endif

 #ifndef LIBPNG_UNIFIED
-#include "png.h"
+#include <png.h>
 #define PNGCRUSH_TIMER_UINT_API extern unsigned int PNGAPI
 #define PNGCRUSH_TIMER_VOID_API extern void PNGAPI
 #else

We force finding png.h through -I includes instead of through the file system.