I don't claim to understand libpng, but I see that it goes out of its way not to overwrite the final bits. This is the commit that introduced the change 15 years ago: https://github.com/pnggroup/libpng/commit/fb5b3ac013b3ea6bf7f32871be75132380abbccd They even added a test to make sure that the bits are not overwritten.
Are you positive that the patch has no other side effects? I couldn't find the issue that prompted the change, but the behaviour is so intentional... Vincenzo On Sat, 16 May 2026 at 18:30, Norbert Preining <[email protected]> wrote: > On Sat, 16 May 2026, Hilmar Preuße wrote: > > I rebuilt the Debian libpng package with the patch in place and > installed it > > into my test chroot, the pdftex binary is linked with the lib in that > > package. The consequential pdflatex runs still generate pdf files with > > different check sums. > > Hmmm, that is strange. I committed a test program, too, into the TeX > Live sources. > > I will rebuild again and see what is going on. > > Best regards > > Norbert > > -- > DI Dr Norbert Preining https://www.preining.info > arXiv / Cornell University + IFMGA Guide + TU Wien + TeX Live > GPG: 0x860CDC13 fp: F7D8 A928 26E3 16A1 9FA0 ACF0 6CAC A448 860C DC13 >
