POINTER_INDEXING was a build configuration option that we maintained
in order to work around a gcc 2.7.2.2 code generation bug (circa 1997).
This provided array-indexing fallback loops in `png_write_PLTE` and
`png_write_sPLT`.
Unfortunately, the fallback paths were effectively untested dead code
in every default build, and have been a recurring source of latent bugs.
(See commit 48800443eb in pnggroup/libpng#801 and commit f27592a0cd in
libpng 1.5.2rc02).
No compiler in current use requires this accommodation.
This is a cherry-pick of commit 28cb99fe65
from branch 'libpng18'.
A funny thing happened while refactoring the function argument parsing
in the `PNGGenConfig` module: the processing of dependencies inside
the CMake function `generate_copy` got fixed, thanks to an inadvertent
typo correction!
Going down the rabbit hole, we uncovered two issues:
1. A typo in `scripts/cmake/PNGGenConfig.cmake` caused a dependency
declaration to disappear, disrupting the graph. Fortunately, this
disruption was being mitigated by an additional set of (redundant)
symbolic target declarations that kept the CMake build going.
2. The exact string matching inside `scripts/cmake/gensrc.cmake.in`
imposed an artificial limitation, disallowing the use of absolute
file paths.
The typo correction in (1), and the use of regex matching instead of
exact string matching in (2), allowed us to use absolute file paths
in the main CMake file, consistently, thus allowing CMake to recognize
them as uniquely-identifiable nodes in the dependency graph. There
should be no further need to have extra symbolic targets for proper
node identification.
In the end, we shaved off the redundant symbolic target declarations,
retaining only `png_genfiles` and `png_genprebuilt`.
When cross compiling for an apple platform on a non-apple platform
(or the reverse), `if(APPLE)` in line 32 should refer to the target
platform. Without importing the `APPLE` variable, it refers to the
host platform.
Reviewed-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
Running the pnglibconf scripts (script/*.awk) is not always possible.
An AWK interpreter is not always guaranteed to be available; and even
if it is, there are limitations when making cross-platform libpng
builds, especially when the differences between the host platform and
the target platform are significant. For example:
* Building for the Windows (MinGW) target on a Unix development host;
* Building for the iOS target on a macOS development host;
* Building for the Android target on any development host.
In such scenarios, a preconfigured (i.e. prebuilt) pnglibconf.h file,
either taken from the libpng source tree or provided by the user who
wants to make a custom libpng build, becomes a necessity.
In this commit we introduce the build option `PNG_LIBCONF_HEADER` in
order to address this specific use case.
We also specify a version range (3.14...4.0) for the minimum required
CMake program, to future-proof the CMake build for just a little bit
longer.
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
This is a major change required by the new PNGv3 colour chunk precedence
rules. It **does not** change the libpng API (png.h) however it changes
the following handling of PNG files:
IFF the PNG file contains colour space information it changes from the
libpng v3 behaviour to the now compulsory PNG v3 behaviour:
1) libpng no longer invalidates colour space chunks because they are
inconsistent.
2) libpng no longer responds to the "png_get_" APIs positively if they
are not present in the PNG but can be deduced from the colour space
chunks that are present.
Add various missing pieces to their right places:
* Update .editorconfig in order to let editorconfig-checker know that
aclocal.m4 (which is auto-generated) may contain trailing whitespace.
* Add ci/README.md.
* Update scripts/README.txt.
TODO:
Integrate editorconfig-checker into the linting workflow on GitHub.
(See .github/workflows/lint.yml)
Apply the following updates:
* Tidy up the compiler flag definitions.
* Update the Darwin, Linux and MSYS makefiles to match the compiler
flags used in scripts/makefile.clang and scripts/makefile.gcc.
* Add the `pngtest-static` target in the Darwin makefile, following
on the Linux makefile.
* Rewrite some of the implicit make rules to match one another more
consistently.
* Make corrections in the copyright years to match git log.
Add scripts/makefile.c89 and refactor scripts/makefile.emcc,
scripts/makefile.clang and scripts/makefile.gcc
Refactor variable definitions inside scripts/makefile.clang,
scripts/makefile.gcc and scripts/makefile.emcc, and start using
the option `-pedantic-errors` unconditionally. This option was
first implemented in GCC version 3.1, and it was available in
Clang and in other Clang-based compilers (e.g. Emscripten) from
the beginning.
Add scripts/makefile.c89, derived from the above makefiles, but
with `-pedantic-errors -std=c89`. We aren't enabling the C89 level
by default, to avoid any incompatibility, whether intentional or
accidental, with the compiler's default language level. However,
we are still continuing to support C89 in the 'libpng16' branch,
and this special makefile can be used for testing purposes.
Apart from the png.h change, these files are machine-generated.
Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
This adds APIs to get/set the two remaining new PNG-v3 colour space
chunks. The mDCV API matches that of cHRM. Both chunks support
floating point APIs (all values in the two chunks are real numbers).
Both chunks have a new encoded type, a four-digit-precision fixed-point
number, which cannot be represented in the existing `png_fixed_point`
type, so a `png_uint_32` is used.
Test examples for cICP, cLLI and mDCV are now in pngtest.png, and a
necessary change to the pngunknown.c test program has been made to
accomodate the additions.
Reviewed-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: John Bowler <jbowler@acm.org>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>
In preparation for the upcoming changes in the build system, any parts
of the CMake file that are unlikely to be affected should be moved out
of the way. This should facilitate an easier resync between the branch
'libpng16' and its successor(s).
Specifically:
* Move the functions `generate_chk`, `generate_out`, `generate_source`
and `generate_copy` to scripts/cmake/PNGGenConfig.cmake.
* Move the function `png_add_test` to scripts/cmake/PNGTest.cmake.
* Leave the function `create_symlink` in place, but add a TODO note.
As we raised the minimum required CMake version to 3.14, we should
now be able to use CMake's built-in function instead.
Apply the following corrections and improvements:
* Add a validity check in `png_set_cICP`.
* Fix the ordering check in `png_handle_cICP`.
* Add a multiplicity check in `png_handle_cICP`.
* Optimize the implementation of `png_write_cICP`.
* Remove an unnecessary preprocessor guard from pngtest.c.
* Update the dependency declaration in pnglibconf.dfa.
* Fix the indentation where necessary.
This is a cherry-pick of commit c2a02691df1ecf51b7c97142752a7034350cb1f6
from branch 'libpng18'.
