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strict_differential: the pixel differential is silently off because its renderer probe expects 1 and gfx_open returns true

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Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
78/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
c, shell
Domain
build-system, testing-qa

Research direction

Start with the renderer probe comparison near line 1593 in tools/strict_differential.sh, then review tests/test_asan_gfx.sh only as related context because that part belongs to #1723. Update the script so only false disables pixel identity, while true runs the differential and any other output fails. Verify the pixel rows run on a working renderer and that a planted gfx_read fault makes the script exit nonzero.

Written by the indexing model from the issue text.

Description

area:gates area:gfx found-by:critic kind:gate-defect

Found while verifying the #1758 R1.2 builder's fix on PR #1776 (phase2-numbers, commit 95ce2fed). On main, nothing has changed.

Since gfx_open returns a bool (#1637), print of (gfx_open of [8, 8, "pixdiff-probe"]) prints true. tools/strict_differential.sh:1593 still compares the probe's last line with "1". So on a machine with a working renderer it sets NO_RENDERER=1, prints NOTE: no renderer — pixel identity is OFF, and finishes OK without running the pixel differential.

Checked on main 0740af03: the probe prints true on Xvfb :99 and with SDL_VIDEODRIVER=dummy. The line is unchanged on origin/main 540f0bcf.

The builder's one-time plant on the branch: a pixel fault in gfx_read passed the old checker (exit 0, pixel rows skipped) and failed the fixed one (37/37 pixel rows differing).

tests/test_asan_gfx.sh's grep "sdl-present: 1" has the same cause; that half is #1723.

Done when

  • On main, tools/strict_differential.sh runs its pixel differential whenever the probe prints true, and fails, rather than reporting "no renderer", on any probe output other than true or false.
  • Planted fault, in the PR: a pixel fault in gfx_read makes tools/strict_differential.sh exit nonzero on a machine with a renderer; restored, it exits 0 with the pixel rows counted.
Dominant language
C
Stars
3
Forks
7
Avg merge
11h 28m
Merged PRs (30d)
262

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