09158: bgfx video causes assertion failure on start when using x87 floating point

ID	Category [?]	Severity [?]	Reproducibility	Date Submitted	Last Update
09158	Crash/Freeze	Minor	Always	15 days ago	14 days ago

Tester	cuavas	View Status	Public	Platform	MAME (Self-compiled)
Assigned To		Resolution	Open	OS	Windows 10/11 (64-bit)
Status [?]	Acknowledged			Driver
Version	0.277	Fixed in Version		Build	32-bit
		Fixed in Git Commit		Github Pull Request #

Summary	09158: bgfx video causes assertion failure on start when using x87 floating point
Description	After updating ImGUI to 1.91.9b, using -video bgfx in a debug build using x87 floating point will result in the following assertion failure on start: Assertion failed: dy >= 0, file ../../../../../3rdparty/bgfx/3rdparty/stb/stb_truetype.h, line 3160 This is presumably due to x87 floating point using 80-bit precision for intermediate results, and hence giving different results to other floating point units. Osso was the biggest proponent of updating ImGUI, so perhaps he wants to look at it or report upstream to the ImGUI project?
Steps To Reproduce	1. Compile MAME with x87 floating point maths (e.g. a 32-bit i686 build without enabling SSE or using the -mfpmath=387 option with GCC). 2. Start any system with -video bgfx. 3. MAME fails to start with an assertion failure.
Additional Information
Github Commit

Flags
Regression Version	0.277
Affected Sets / Systems

Attached Files