Deimplementing complications in libpng18

[ctruta]

Here are three honking commits for your viewing and reviewing pleasure.

FYI, projects/owatcom and scripts/makefile.intel are about to go, because they depend on what I'm about to remove in this PR. And I could fix those but I ain't gonna. And CMake should be able to do their job, anyway. I haven't tested Open Watcom recently, but last time I did give it a try, about two years ago, its IDE died a horrible death when I attempted to do stuff with projects/owatcom on my Windows 10 laptop.

Also about Watcom: fun fact: I used to live and work in Waterloo, Ontario for aboot a decade, and two former Watcom compiler engineers used to be in my team at BlackBerry for a while. Because, you know... Waterloo... compiler... wink-wink 😉

[ctruta]

@jbowler I wanted to add you in as a reviewer, but you being in and out of this group resulted in me having to summon you hereby, because GitHub's "Reviewers" feature doesn't let me add you in there.

[jbowler]

Looks good. Mostly copy edit so it should be fine if it compiles. I can't test the maybe-significant change which is the removal of PNGAPI/PNGCBAPI; they were always no-ops on the systems I use. PNGFAPI looks fine but I need to do a gh pr pull and check the minconfigs; again any issues will be fail-to-compile, not some fundamental problem with the change.

[jbowler]

The configure build fails (on AMD64) thus:

rm -f pnglibconf.c pnglibconf.tf[45]
rm -f scripts/pnglibconf/symbols.out scripts/pnglibconf/symbols.tf[12]
make: *** No rule to make target 'scripts/pnglibconf/symbols.def', needed by 'scripts/pnglibconf/symbols.chk'.  Stop.

The cmake build doesn't try to build it (I think you removed it), however it fails thus:

     -g -O2 --std=c90 -pedantic -Wcast-align -Wshadow -Werror -fPIC -MD -MT CMakeFiles/png_shared.dir/pngwutil.c.o -MF CMakeFiles/png_shared.dir/pngwutil.c.o.d -o CMakeFiles/png_shared.dir/pngwutil.c.o -c /home/jbowler/src/libpng/github/git/pngwutil.c
In file included from /home/jbowler/src/libpng/github/git/pngpriv.h:205,
                 from /home/jbowler/src/libpng/github/git/png.c:13:
/home/jbowler/src/libpng/github/git/png.h:1039:43: error: ISO C does not allow extra ‘;’ outside of a function [-Werror=pedantic]
 1039 |     png_const_timep ptime),PNG_DEPRECATED);

I.e. that pesky macro again.

[jbowler]

cmake is fixed by removing the three(?) spurious ";" characters from the end of the PNG_REMOVED macros in png.h.

configure build is fixed by changing Makefile.am to refer to scripts/symbols.def, not scripts/pnglibconf/symbols.def. (Maybe none of the "symbols" stuff should be in scripts/pnglibconf, i.e. not symbols.c, checksym.awk but it looks like you intended symbols.def to be there too).

The configure "make check" fails at pngtest-all, which is weird, but there is not corresponding cmake test so far as I can see. It fails on:

pngtest contrib/testpngs/badpal/test-palette-8.png

Because the error message that is emitted:

libpng error: Wrote palette index exceeding num_palette

Doesn't seem to be found:

MISSING REPORT: contrib/testpngs/badpal/test-palette-8.png: IDAT: Read palette index exceeding num_palette
rwrwrwrwrwrwrwrwrwrwrwrwrwrwrwrw=============== FAIL(EXPECTED) contrib/testpngs/badpal/test-palette-8.png ====================
MISSING REPORT: contrib/testpngs/badpal/test-palette-8.png: Wrote palette index exceeding num_palette
FAIL tests/pngtest-all (exit status: 1)

[jbowler]

You removed STDERR from pngtest.c, so now the output does not go to stdout.

EDIT: redirecting to stdout fixes the problem.

[jbowler]

With those changes (Makefile.am scripts.def, png.h PNG_REMOVED and tests/pngtest-all 2>&1 in TEST) the base builds all pass except for aarch64. The latter is not new; the assembler does not compile with -pedantic, from cmake:

In file included from /home/jbowler/src/libpng/github/git/arm/arm_init.c:78,
                 from /home/jbowler/src/libpng/github/git/pngsimd.c:57:
/home/jbowler/src/libpng/github/git/arm/palette_neon_intrinsics.c: In function ‘png_riffle_palette_neon’:
/home/jbowler/src/libpng/github/git/arm/palette_neon_intrinsics.c:21:7: error: initializer element is not computable at load time [-Werror=pedantic]
   21 |       vdupq_n_u8(0x00),
      |       ^~~~~~~~~~
/home/jbowler/src/libpng/github/git/arm/palette_neon_intrinsics.c:22:7: error: initializer element is not computable at load time [-Werror=pedantic]
   22 |       vdupq_n_u8(0x00),
      |       ^~~~~~~~~~
/home/jbowler/src/libpng/github/git/arm/palette_neon_intrinsics.c:23:7: error: initializer element is not computable at load time [-Werror=pedantic]
   23 |       vdupq_n_u8(0x00),
      |       ^~~~~~~~~~
/home/jbowler/src/libpng/github/git/arm/palette_neon_intrinsics.c:24:7: error: initializer element is not computable at load time [-Werror=pedantic]
   24 |       vdupq_n_u8(0xff),
      |       ^~~~~~~~~~
/home/jbowler/src/libpng/github/git/arm/palette_neon_intrinsics.c:20:22: error: initializer element is not computable at load time [-Werror=pedantic]
   20 |    uint8x16x4_t w = {{
      |                      ^
/home/jbowler/src/libpng/github/git/arm/arm_init.c: In function ‘png_target_do_expand_palette_neon’:
/home/jbowler/src/libpng/github/git/arm/arm_init.c:148:10: error: ISO C90 forbids mixed declarations and code [-Werror=declaration-after-statement]
  148 |          png_bytep dp = row + (4/*RGBA*/*row_width - 1);
      |          ^~~~~~~~~

It's the same in libpng-1.6, I've been ignoring it.

[jbowler]

The "minconfig" builds with configure seem to be as expected. The ones with cmake seem to have stopped working - it looks like everything gets built.

[jbowler]

cmake "minconfig" builds seem consistent too; I had typo'ed (or probably edito'ed) DFA_XTRA to DFA_XTA on the command line for cmake. I did notice that despite setting 'VERBOSE=1' on the corresponding "make" the cmake sub-command doesn't seem to generate any output - the cmake for OUTPUT=pnglibconf.h is recorded in the log file but not the executed commands.

[jbowler]

My three fixes are in #660