Try to build with USE="debug" and launch in console

you have tried disable flash plugin?

I didn't install flash.
I try debug option.

Alexander Pilipenko wrote:

Try to build with USE="debug" and launch in console

With debug FLAG it's very difficult to surf on the Internet.

When I click on a link, the page is displayed 3 or 4 seconds after ... it's very long and i can't use Firefox with that.

Each time I click on a link, some lines displayed on my console :

--DOMWINDOW == 187 (0x7f2982feec00) [pid = 8717] [serial = 453] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 186 (0x7f295b1df000) [pid = 8717] [serial = 456] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 185 (0x7f29ce55cc00) [pid = 8717] [serial = 468] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 184 (0x7f295bc6ac00) [pid = 8717] [serial = 465] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 183 (0x7f29600e3c00) [pid = 8717] [serial = 462] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 182 (0x7f2982fef800) [pid = 8717] [serial = 454] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 181 (0x7f295f610c00) [pid = 8717] [serial = 457] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 180 (0x7f29d3522400) [pid = 8717] [serial = 469] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 179 (0x7f295bc6c400) [pid = 8717] [serial = 466] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 178 (0x7f29600ed000) [pid = 8717] [serial = 463] [outer = (nil)] [url = about:blank]
++DOMWINDOW == 179 (0x7f295c33a800) [pid = 8717] [serial = 474] [outer = 0x7f29b556a000]
[8717] WARNING: Image width or height is non-positive: file /var/calculate/tmp/portage/www-client/firefox-43.0/work/firefox-43.0/layout/base/nsLayoutUtils.cpp, line 6277

It didn't take long ...

++DOMWINDOW == 87 (0x7ff30b8b3000) [pid = 19252] [serial = 747] [outer = 0x7ff333ba8400]
[19252] WARNING: Image width or height is non-positive: file /var/calculate/tmp/portage/www-client/firefox-43.0/work/firefox-43.0/layout/base/nsLayoutUtils.cpp, line 6277
JavaScript error: http://www.mageialinux-online.org/kernel/lib/js/mlo/sequence/sequence.js, line 22: TypeError: sequence is undefined
--DOCSHELL 0x7ff309f57800 == 39 [pid = 19252] [id = 344]
--DOCSHELL 0x7ff313cf8800 == 38 [pid = 19252] [id = 348]
--DOCSHELL 0x7ff3126c1800 == 37 [pid = 19252] [id = 347]
--DOMWINDOW == 86 (0x7ff310ece800) [pid = 19252] [serial = 578] [outer = 0x7ff3072c7c00] [url = about:blank]
--DOMWINDOW == 85 (0x7ff313a04800) [pid = 19252] [serial = 740] [outer = 0x7ff30ab52000] [url = about:blank]
--DOMWINDOW == 84 (0x7ff30ab52000) [pid = 19252] [serial = 739] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 83 (0x7ff3072c7c00) [pid = 19252] [serial = 577] [outer = (nil)] [url = about:blank]
--DOMWINDOW == 82 (0x7ff3116b9c00) [pid = 19252] [serial = 732] [outer = (nil)] [url = https://twitter.com/i/cards/tfw/v1/650088036802269184?advertiser_name=MuleSoft&cardname=summary_large_image&is_following_advertiser=false&impression_id=59140185c1c02cfa&lang=fr#xdm_e=https%3A%2F%2Ftwitter.com&xdm_c=default6587&xdm_p=1]
++DOMWINDOW == 83 (0x7ff30ab56c00) [pid = 19252] [serial = 748] [outer = 0x7ff333ba8400]
[19252] WARNING: Image width or height is non-positive: file /var/calculate/tmp/portage/www-client/firefox-43.0/work/firefox-43.0/layout/base/nsLayoutUtils.cpp, line 6277
[19252] WARNING: RasterImage::Init failed: file /var/calculate/tmp/portage/www-client/firefox-43.0/work/firefox-43.0/image/ImageFactory.cpp, line 109
JavaScript error: http://www.mageialinux-online.org/kernel/lib/js/mlo/sequence/sequence.js, line 22: TypeError: sequence is undefined

Program firefox (pid = 19252) received signal 11.
Stack:
#01: ???[/usr/lib64/firefox/libxul.so +0x2f92ef1]
#02: ???[/lib64/libpthread.so.0 +0x10740]
#03: ???[/usr/lib64/firefox/libxul.so +0x3230ecd]
#04: ???[/usr/lib64/firefox/libxul.so +0x31e6c9a]
#05: ???[/usr/lib64/firefox/libxul.so +0x362fba0]
#06: ???[/usr/lib64/firefox/libxul.so +0x363ebe0]
#07: ???[/usr/lib64/firefox/libxul.so +0x363fbfe]
#08: ???[/usr/lib64/firefox/libxul.so +0x3640142]
#09: ???[/usr/lib64/firefox/libxul.so +0x3641e8a]
#10: ???[/usr/lib64/firefox/libxul.so +0x16c38e0]
#11: ???[/usr/lib64/firefox/libxul.so +0xacea7a]
#12: ???[/usr/lib64/firefox/libxul.so +0xac5efc]
#13: ???[/usr/lib64/firefox/libxul.so +0xac23ff]
#14: ???[/usr/lib64/firefox/libxul.so +0xaf13aa]
#15: ???[/usr/lib64/firefox/libxul.so +0xd93ca1]
#16: ???[/usr/lib64/firefox/libxul.so +0xd68978]
#17: ???[/usr/lib64/firefox/libxul.so +0xd689cd]
#18: ???[/usr/lib64/firefox/libxul.so +0x2571ad1]
#19: ???[/usr/lib64/firefox/libxul.so +0x2d656f5]
#20: ???[/usr/lib64/firefox/libxul.so +0x2dbf734]
#21: ???[/usr/lib64/firefox/libxul.so +0x2dbf9cf]
#22: XRE_main[/usr/lib64/firefox/libxul.so +0x2dbfc1f]
#23: ???[firefox +0x536a]
#24: ???[firefox +0x4b8a]
#25: __libc_start_main[/lib64/libc.so.6 +0x20850]
#26: _start[firefox +0x4cb9]
#27: ??? (???:???)
Sleeping for 300 seconds.
Type 'gdb firefox 19252' to attach your debugger to this thread.
Processus arrêté

Recently I began to use Firefox on Android. Yes, he occasionally falls! )

I have similar issue with www-client/firefox-43.0 (marked as ~arch): random crashes, sometimes during video (no flash plugin), sometimes on pages with infinite scrolling. Version from package www-client/firefox-bin-43.0 seems to work fine.

Similar issue: http://www.calculate-linux.ru/issues/827

I found the solution :

In about:config :
layers.offmainthreadcomposition.async-animations -> false
layers.offmainthreadcomposition.enabled -> false

USE :
www-client/firefox -system-cairo

Thank you, Adrien! With the corrected flag seems to be no problem.