Bad FontBBox set on existing font when using pdftocairo
I tried to run a pdf through pdftocairo in order to embed some non embedded fonts to ready a file for sending off to a printer. The fonts embedded just fine, however of the fonts that were already embedded one (helvetica) was assigned a new negative bbox.
While that doesn't appear to cause any issues with appearance it does cause adobe reader to throw up a BLABLA_Helvetica contains a bad /BBox message box.
I checked the original file and the font in there has FontBBox[ -951 -481 1446 1122]
I checked the file after pdftocairo and it's /FontBBox [ 31049 -480 1445 1121 ]
I edited the resulting file to [ -951 -480 1445 1121 ] and the error is gone, to be sure I diff checked the output and all 3 are visually identical.
Looking at those numbers it seems to me there is a fairly simple int -> uint type thing slipping through (32000-951 being 31049)
Attached a before and after of pdftocairo -pdf P11_safe.pdf P11_cairo.pdf
The contents of the pdfs have been deliberately scraped of bits of sensitive text so that I could upload it.