[FIX]: Fix libpng ARM source inclusion for non-Darwin AArch64 CMake builds

[x15sr71]

In raising this pull request, I confirm the following (please check boxes):

Reason for this PR:

• This PR adds new functionality.
• This PR fixes a bug that I have personally experienced or that a real user has reported and for which a sample exists.
• This PR is porting code from C to Rust.

Sanity check:

• I have read and understood the contributors guide.
• I have checked that another pull request for this purpose does not exist.
• If the PR adds new functionality, I've added it to the changelog. If it's just a bug fix, I have NOT added it to the changelog.
• I am NOT adding new C code unless it's to fix an existing, reproducible bug.

Repro instructions:

• Reproduced the failure while building CCExtractor with CMake on Linux AArch64 (Ubuntu 24.04, GCC 13.3, CMake 3.28) using the pre-fix CMakeLists.txt.

---

Issue

Building CCExtractor from source with CMake on Linux AArch64 (Ubuntu 24.04, GCC 13.3, CMake 3.28) fails at link time:

/usr/bin/ld: pngrtran.c: undefined reference to `png_do_expand_palette_rgba8_neon'
/usr/bin/ld: pngrtran.c: undefined reference to `png_do_expand_palette_rgb8_neon'
/usr/bin/ld: pngrtran.c: undefined reference to `png_riffle_palette_neon'
/usr/bin/ld: pngrutil.c: undefined reference to `png_init_filter_functions_neon'
collect2: error: ld returned 1 exit status

The identical commit builds cleanly on Apple Silicon macOS.

Root Cause

Bundled libpng (thirdparty/libpng/pngpriv.h) auto-enables ARM NEON code paths (PNG_ARM_NEON_OPT=2) whenever the compiler defines __ARM_NEON/ __ARM_NEON__ — which GCC/clang do unconditionally on any aarch64 target, since NEON is mandatory in the AArch64 ISA. This causes pngrtran.c and pngrutil.c to reference NEON symbols regardless of OS.

However, src/CMakeLists.txt only compiled the NEON implementation sources (thirdparty/libpng/arm/*.c) under Darwin + arm64:

if (${CMAKE_SYSTEM_NAME} MATCHES "Darwin")
  if(${CMAKE_HOST_SYSTEM_PROCESSOR} MATCHES "arm64")
    include_directories(${PROJECT_SOURCE_DIR}/thirdparty/libpng/arm)
    aux_source_directory(${PROJECT_SOURCE_DIR}/thirdparty/libpng/arm SOURCEFILE)
  else()
    include_directories("/usr/local/include")
  endif()
endif()

On Linux AArch64 the symbols are referenced but never defined, producing the undefined-reference errors above.

Fix

Split the OS-specific include-path logic from the architecture-specific source-selection logic, and gate the latter on the target processor (CMAKE_SYSTEM_PROCESSOR) rather than host + OS:

# ARM libpng sources
if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm64|aarch64)$")
    include_directories(${PROJECT_SOURCE_DIR}/thirdparty/libpng/arm)
    aux_source_directory(${PROJECT_SOURCE_DIR}/thirdparty/libpng/arm SOURCEFILE)
endif()

# macOS include paths
if(CMAKE_SYSTEM_NAME MATCHES "Darwin")
    if(CMAKE_SYSTEM_PROCESSOR MATCHES "^(arm64|aarch64)$")
        include_directories("/opt/homebrew/include")
    else()
        include_directories("/usr/local/include")
    endif()
endif()

CMAKE_SYSTEM_PROCESSOR (target arch) is used instead of CMAKE_HOST_SYSTEM_PROCESSOR (build-machine arch), which is also the technically correct variable for this decision and fixes a latent cross-compilation bug in the original code (host arch and target arch only happened to match for native builds).

Behavior on macOS Intel, Apple Silicon, and Linux x86_64 is unchanged.

Testing

• Reproduced the failure on Linux AArch64 (Ubuntu 24.04, GCC 13.3, CMake 3.28) with the original CMake configuration.
• Applied this patch and performed a clean rebuild
• Verified that the bundled libpng ARM NEON sources are now compiled into the build by confirming the generated object files (e.g. filter_neon_intrinsics.c.o and palette_neon_intrinsics.c.o), which were absent before the change.
• Confirmed the previous undefined NEON linker errors no longer occur.
• Verified the resulting binary by running, it executes successfully and prints the expected version information.

[ccextractor-bot]

CCExtractor CI platform finished running the test files on linux. Below is a summary of the test results, when compared to test for commit 2feb09a...:

Report Name	Tests Passed
Broken	9/13
CEA-708	2/14
DVB	1/7
DVD	3/3
DVR-MS	2/2
General	23/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	68/86
Teletext	20/21
WTV	12/13
XDS	31/34

Your PR breaks these cases:

• ccextractor --out=srt --latin1 611b4a9235...
• ccextractor --autoprogram --out=ttxt --latin1 1020459a86...
• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2...
• ccextractor --autoprogram --out=ttxt --latin1 99e5eaafdc...
• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65...
• ccextractor --autoprogram --out=ttxt --latin1 01509e4d27...
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b...
• ccextractor --in=ts c83f765c66...
• ccextractor --out=srt c83f765c66...
• ccextractor --out=spupng c83f765c66...
• ccextractor --utf8 c83f765c66...
• ccextractor --dru c83f765c66...
• ccextractor --startat 4 --endat 7 c83f765c66...
• ccextractor --codec dvbsub --out=spupng 85271be4d2...
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --tpage 801 4e56e88ba4...
• ccextractor --out=srt --latin1 f23a544ba8...
• ccextractor --autoprogram --out=srt --latin1 --ucla d037c7509e...
• ccextractor --autoprogram --out=srt --latin1 --ucla 7d3f25c32c...
• ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 7f41299cc7...

NOTE: The following tests have been failing on the master branch as well as the PR:

• ccextractor --out=srt --latin1 --autoprogram 73d9313d64..., Last passed:

  Test 8738

• ccextractor --out=ttxt --latin1 001dd8cdf7..., Last passed:

  Test 8738

• ccextractor --out=srt --latin1 4d4e938ef6..., Last passed:

  Test 8738

• ccextractor --service 1 --out=txt --no-bom --no-rollup ea83ff7bcb..., Last passed:

  Test 8738

• ccextractor --service 1 --out=txt f17524b53f..., Last passed:

  Test 8738

• ccextractor --service 1 --out=txt 80848c45f8..., Last passed:

  Test 8738

• ccextractor --service 1 --out=txt --no-bom --no-rollup b5d6aad89f..., Last passed:

  Test 8738

• ccextractor --service 1[EUC-KR] --out=txt --no-rollup b5d6aad89f..., Last passed:

  Test 8738

• ccextractor --service 1 --out=srt da904de35d..., Last passed:

  Test 8738

• ccextractor --service 1 --out=sami da904de35d..., Last passed:

  Test 8738

• ccextractor --service 1[EUC-KR] b5d6aad89f..., Last passed:

  Test 8738

• ccextractor --service 1[EUC-KR] --no-rollup b5d6aad89f..., Last passed:

  Test 8738

• ccextractor --service all da904de35d..., Last passed:

  Test 8738

• ccextractor --service all[EUC-KR] b5d6aad89f..., Last passed:

  Test 8738

• ccextractor --service 1,2[UTF-8],3[EUC-KR],54 --out=txt da904de35d..., Last passed:

  Test 8738

• ccextractor --autoprogram --out=srt --latin1 f1422b8bfe..., Last passed:

  Test 9208

• ccextractor --autoprogram --out=srt --latin1 d41b53b504..., Last passed:

  Test 8738

• ccextractor --stdout --quiet --no-fontcolor 79a51f3500..., Last passed:

  Test 8738

• ccextractor --stdout --quiet --no-fontcolor 767b546f96..., Last passed:

  Test 8738

• ccextractor --service 1 c83f765c66..., Last passed:

  Test 8738

• ccextractor --myth c83f765c66..., Last passed:

  Test 8738

• ccextractor --in=raw fb79021542..., Last passed:

  Test 8738

• ccextractor --mp4vidtrack 5df914ce77..., Last passed:

  Test 8738

• ccextractor --xmltv=3 --out=null 96efd279cf..., Last passed:

  Test 8738

• ccextractor --datapid 2310 --autoprogram --out=srt --latin1 e639e54550..., Last passed:

  Test 8738

Congratulations: Merging this PR would fix the following tests:

• ccextractor --service 1 --out=ttxt da904de35d..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 132d7df7e9..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 b22260d065..., Last passed: Never

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

Check the result page for more info.

[ccextractor-bot]

CCExtractor CI platform finished running the test files on windows. Below is a summary of the test results, when compared to test for commit 9f78685...:

Report Name	Tests Passed
Broken	10/13
CEA-708	2/14
DVB	2/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	78/86
Teletext	20/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2...
• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65...
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b...
• ccextractor --out=spupng c83f765c66...
• ccextractor --codec dvbsub --out=spupng 85271be4d2...
• ccextractor --teletext 4e56e88ba4...

NOTE: The following tests have been failing on the master branch as well as the PR:

• ccextractor --out=srt --latin1 --autoprogram 73d9313d64..., Last passed:

  Test 8611

• ccextractor --out=ttxt --latin1 001dd8cdf7..., Last passed:

  Test 8611

• ccextractor --out=srt --latin1 4d4e938ef6..., Last passed:

  Test 8611

• ccextractor --service 1 --out=txt --no-bom --no-rollup ea83ff7bcb..., Last passed:

  Test 8611

• ccextractor --service 1 --out=txt f17524b53f..., Last passed:

  Test 8611

• ccextractor --service 1 --out=txt 80848c45f8..., Last passed:

  Test 8611

• ccextractor --service 1 --out=txt --no-bom --no-rollup b5d6aad89f..., Last passed:

  Test 8611

• ccextractor --service 1[EUC-KR] --out=txt --no-rollup b5d6aad89f..., Last passed:

  Test 8611

• ccextractor --service 1 --out=srt da904de35d..., Last passed:

  Test 8611

• ccextractor --service 1 --out=sami da904de35d..., Last passed:

  Test 8611

• ccextractor --service 1[EUC-KR] b5d6aad89f..., Last passed:

  Test 8611

• ccextractor --service 1[EUC-KR] --no-rollup b5d6aad89f..., Last passed:

  Test 8611

• ccextractor --service all da904de35d..., Last passed:

  Test 8611

• ccextractor --service all[EUC-KR] b5d6aad89f..., Last passed:

  Test 8611

• ccextractor --service 1,2[UTF-8],3[EUC-KR],54 --out=txt da904de35d..., Last passed:

  Test 8611

• ccextractor --autoprogram --out=srt --latin1 f1422b8bfe..., Last passed:

  Test 9209

• ccextractor --autoprogram --out=srt --latin1 d41b53b504..., Last passed:

  Test 8611

• ccextractor --stdout --quiet --no-fontcolor 79a51f3500..., Last passed:

  Test 8611

• ccextractor --stdout --quiet --no-fontcolor 767b546f96..., Last passed:

  Test 8611

• ccextractor --service 1 c83f765c66..., Last passed:

  Test 8611

• ccextractor --myth c83f765c66..., Last passed:

  Test 8611

• ccextractor --in=raw fb79021542..., Last passed:

  Test 8611

• ccextractor --mp4vidtrack 5df914ce77..., Last passed:

  Test 8611

• ccextractor --xmltv=3 --out=null 96efd279cf..., Last passed:

  Test 8611

• ccextractor --datapid 2310 --autoprogram --out=srt --latin1 e639e54550..., Last passed:

  Test 8611

Congratulations: Merging this PR would fix the following tests:

• ccextractor --out=srt --latin1 611b4a9235..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 1020459a86..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 132d7df7e9..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 99e5eaafdc..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 01509e4d27..., Last passed: Never
• ccextractor --dru c83f765c66..., Last passed: Never
• ccextractor --startat 4 --endat 7 c83f765c66..., Last passed: Never
• ccextractor --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsnotbefore 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --out=srt --latin1 f23a544ba8..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --ucla d037c7509e..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --ucla 7d3f25c32c..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 --ucla --xds 7f41299cc7..., Last passed: Never

It seems that not all tests were passed completely. This is an indication that the output of some files is not as expected (but might be according to you).

Check the result page for more info.