Iphone - device - linker error

Question

I have added libpng to my application. If I build for simulator, everything is OK. When I build application for device, I got linker error:

    Undefined symbols for architecture armv7: "_png_init_filter_functions_neon", referenced from: _png_read_filter_row in libpng-arm7-release.a(pngrutil.o)

I have build libpng manually from source, same way for simulator and device (only with changed target of compilation). I have tried to find this problem, but noone seems to post anything about this problem.

score 10 · Accepted Answer · answered Oct 03 '13 at 07:34

10

I "solved" this by replacing lines 117-121 in libpng's pngpriv.h:

#  ifdef __ARM_NEON__
#     define PNG_ARM_NEON_OPT 2
#  else
#     define PNG_ARM_NEON_OPT 0
#  endif

by

#define PNG_ARM_NEON_OPT 0

This disables ARM's NEON optimizations, which seems to be the cause of the problem.

This is merely a workaround though, I didn't have time to investigate the real cause of the problem further.

answered Oct 03 '13 at 07:34

Guillaume Algis

10,705
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2

You need compile *.c files from arm folder. – PSyton Jan 01 '14 at 07:18
3

you can also just compile with preprocessor flag "PNG_ARM_NEON_OPT=0" so you don't have to modify libpng source – CuriousGeorge Mar 24 '14 at 01:22
Do we need to compile *.c after doing change in .h, and how? – Muhammad Raza Mar 09 '16 at 09:49
I have to face the same problem in 3.1.0 version. i am trying to find the file location. Kindly give guide line to find that path of the file. – HariKrishnan.P Jun 15 '16 at 09:22
@HariKrishnan.P not quite sure what you're talking about since there's no version 3.1.0 of libpng. – Guillaume Algis Jun 15 '16 at 09:34
@HariKrishnan.P ... ok, but this question is about libpng. So not sure what you are expecting here :) – Guillaume Algis Jun 15 '16 at 09:39
I try to find the libpng file in my project. but i cannot, so i asking about the libpng file path – HariKrishnan.P Jun 15 '16 at 10:01
`find /path/to/your/project -name 'pngpriv.h'` – Guillaume Algis Jun 15 '16 at 10:08

score 1 · Answer 2 · answered Aug 28 '14 at 11:39

Adding to PSyton's comment, here is how we solved it. Compile the arm/*.c files. This however does only work for Android. For iOS, we additionally had to create a new pnglibconf.h with the entries:

#undef PNG_ARM_NEON_API_SUPPORTED
#undef PNG_ARM_NEON_CHECK_SUPPORTED
#define PNG_ARM_NEON_OPT 0

Looking at the ARM defines in libpng, it seems like they are a bit buggy currently, as PNG_ARM_NEON_API_SUPPORTED should be sufficient to turn NEON compilation off.

score 1 · Answer 3 · answered Feb 10 '23 at 04:48

1

I experienced a similar error on macOS. After getting libpng from the source https://sourceforge.net/projects/libpng/files/ and compiling with the PNG_ARM_NEON option off, the error disappeared.

answered Feb 10 '23 at 04:48

air-h-128k-il

11
1

Iphone - device - linker error

3 Answers3

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