Validate GD::Image initialization before image operations

[damseleng]

Summary

This PR validates GD::Image initialization state before image operations.

It changes invalid or uninitialized image usage from native process crashes to Ruby exceptions, and includes the related text bounding box updates from feature/fix-new-and-tbbox-bugs.

Changes

• Require width and height when creating a new GD::Image
• Raise an exception when image methods are called on an uninitialized image object
• Add defensive checks before image operations that require an initialized image
• Include the related text bounding box changes

Validation

Tested locally on WSL/Ubuntu.

Before the fix, calling image methods on an uninitialized GD::Image instance could crash the Ruby process. After this change, the same cases raise Ruby exceptions instead.

Validated cases:

ruby -Ilib -Iext -rgd -e 'img = GD::Image.new; puts img.width'
# ArgumentError: width and height are required

ruby -Ilib -Iext -rgd -e 'img = GD::Image.allocate; puts img.width'
# RuntimeError: image not initialized

The test suite passes:

bundle exec rspec
# 43 examples, 0 failures

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

This PR hardens GD::Image construction and instance-method safety by rejecting empty initialization, adding NULL-pointer guards, and making text bounding-box measurement side-effect free, along with a version bump and changelog updates.

Changes:

• Require width/height in GD::Image.new and add dimension validation + NULL guards across image operations.
• Fix text_bbox to avoid drawing onto the image during measurement.
• Bump gem version to 0.3.1 and document the changes in CHANGELOG.md.

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
spec/image_spec.rb	Adds specs for .new argument validation and NULL-guard behavior on instance methods.
spec/image/initialize_spec.rb	Updates initialization expectations to require width/height.
ext/gd/image.c	Enforces required dimensions, adds NULL guards, implements initialize_copy, and adjusts constructors/allocation paths.
ext/gd/text.c	Passes NULL image ptr to avoid rendering during bbox calculation.
ruby-libgd.gemspec	Bumps gem version to 0.3.1.
CHANGELOG.md	Documents new safety behavior and text bbox fix (needs formatting fixes).
.gitignore	Ignores aider and notebook artifacts.

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