[FIX] Fix unchecked fopen() and alloc_demuxer_data() return values in process_hex()

[NexionisJake]

• Add NULL check for fopen() return; call fatal() with appropriate
  error code if the file cannot be opened, preventing a segfault on
  fgets().
• Add NULL check for alloc_demuxer_data() return; close the
  already-opened file handle before calling fatal() to avoid a resource
  leak.

Fixes #2201

In raising this pull request, I confirm the following :

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](https://github
  .com/CCExtractor/ccextractor/blob/master/.github/CONTRIBUTING.md).
• 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:

process_hex() in src/lib_ccx/general_loop.c is reachable when
CCExtractor is built with -DWTV_DEBUG and a .hex dump file is passed
as input.

Crash 1 — NULL fopen() (segfault on fgets):

1. Build with -DWTV_DEBUG.
2. Invoke process_hex() with a filename that does not exist or is not
   readable.
3. Without the fix: fr is NULL, and the immediately following
   fgets(line, max-1, fr) dereferences it → segfault.
4. With the fix: fatal(CCX_COMMON_EXIT_FILE_CREATION_FAILED, ...) is
   called with a clear error message before any dereference occurs.

Crash 2 — NULL alloc_demuxer_data() (NULL dereference + fd leak):

1. Build with -DWTV_DEBUG.
2. Trigger an OOM condition (or mock alloc_demuxer_data() to return
   NULL).
3. Without the fix: data is NULL, the loop body writes into
   data->buffer → segfault; fr is also leaked.
4. With the fix: fr is closed first, then
   fatal(EXIT_NOT_ENOUGH_MEMORY, ...) is called cleanly.

The fix is two surgical NULL checks matching the existing error-handling
style used throughout the file (EXIT_NOT_ENOUGH_MEMORY) and the rest
of the project (CCX_COMMON_EXIT_FILE_CREATION_FAILED — same pattern as
ccx_encoders_spupng.c:1137). No other lines were changed.

Note: PR #2202 also addresses this issue but omits the fclose(fr)
before the second fatal() call, leaving a file descriptor leak. This
PR includes that cleanup.

[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 03ad9e8...:

Report Name	Tests Passed
Broken	10/13
CEA-708	1/14
DVB	4/7
DVD	3/3
DVR-MS	2/2
General	27/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	79/86
Teletext	20/21
WTV	13/13
XDS	34/34

Your PR breaks these cases:

• ccextractor --startcreditsnotafter 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...
• ccextractor --startcreditsforatmost 2 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9...

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 --out=ttxt da904de35d..., Last passed:

  Test 8926

• 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 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 --autoprogram --out=ttxt --latin1 --ucla --xds 8e8229b88b..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --quant 0 85271be4d2..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 132d7df7e9..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 99e5eaafdc..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 b22260d065..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 --ucla 7aad20907e..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 --ucla dab1c1bd65..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 01509e4d27..., Last passed: Never
• ccextractor --out=srt --latin1 --autoprogram 29e5ffd34b..., Last passed: Never
• ccextractor --out=spupng 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 --startcreditsforatleast 1 --startcreditstext "CCextractor Start crdit Testing" c4dd893cb9..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --xds --latin1 --ucla 85058ad37e..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --ucla b22260d065..., 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.

[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 03ad9e8...:

Report Name	Tests Passed
Broken	10/13
CEA-708	1/14
DVB	3/7
DVD	3/3
DVR-MS	2/2
General	25/27
Hardsubx	1/1
Hauppage	3/3
MP4	3/3
NoCC	10/10
Options	75/86
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 --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...

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 --out=ttxt da904de35d..., Last passed:

  Test 8943

• 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 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 --autoprogram --out=ttxt --latin1 --ucla --xds 8e8229b88b..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 132d7df7e9..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 99e5eaafdc..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 b22260d065..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 --ucla 7aad20907e..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --latin1 01509e4d27..., Last passed: Never
• ccextractor --autoprogram --out=ttxt --xds --latin1 --ucla 85058ad37e..., Last passed: Never
• ccextractor --autoprogram --out=srt --latin1 --ucla b22260d065..., 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.

[cfsmp3]

Closing — the fopen()/alloc_demuxer_data() NULL checks in process_hex() are now covered by #2202 (just merged). Thanks for the contribution.