Please see the original Tor ticket: https://trac.torproject.org/projects/tor/ticket/26514

libmar uses _ftelli64 and _fseeki64 which was causing updater failures on Tor Browser Win64. The Tor Browser patch uses ftello64 and fseeko64 instead for MinGW.

Avoid MinGW's _ftelli64() and _fseeki64() implementations because they
are unreliable.

Try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=936d5a50c36bbf235e48eae272d60769722bed00

Pushed by dluca@mozilla.com:
https://hg.mozilla.org/integration/autoland/rev/98a5a4864b88
intermittent updater failures on Win64 (Error 19) r=rstrong

https://hg.mozilla.org/mozilla-central/rev/98a5a4864b88

Comment on attachment 9074224 [details]
Bug 1561636 - intermittent updater failures on Win64 (Error 19)

ESR Uplift Approval Request

• If this is not a sec:{high,crit} bug, please state case for ESR consideration: One less patch for Tor Browser to maintain for next ESR
• User impact if declined: Minor
• Fix Landed on Version: 69
• Risk to taking this patch: Low
• Why is the change risky/not risky? (and alternatives if risky): There is code in Firefox already using ftello64 and fseeko64 for __MINGW32__, see https://hg.mozilla.org/mozilla-central/file/04a7c8e2ab6d9be7b4c083ed14104005e4da87b7/media/libvpx/libvpx/tools_common.h#l32.
• String or UUID changes made by this patch: None

Comment on attachment 9074224 [details]
Bug 1561636 - intermittent updater failures on Win64 (Error 19)

Fixes updater issues for MinGW builds used by Tor. Doesn't affect builds we ship. Approved for 68.1esr.

https://hg.mozilla.org/releases/mozilla-esr68/rev/a3ca22e1ef37