swiftlang/swift

[SR-2403] Recognize __builtin_{huge_val,inf,nan}() macros

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#45,010 opened on Aug 18, 2016

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bugc interopc/c++ macroscompilergood first issue

Description
Previous ID SR-2403
Radar rdar://problem/19051485
Original Reporter @belkadan
Type Bug
Votes 0
Component/s Compiler
Labels Bug, ClangImporter, Macros, StarterBug
Assignee None
Priority Medium

md5: c8e64f9c66f50b498cedbe9171dcc5a6

Issue Description:

__builtin_huge_val(), __builtin_nan(""), and __builtin_inf() are often used to define macros that evaluate to IEEE infinity or NaN. We could recognize these patterns and import them as aliases for Double.infinity/nan (or mark them unavailable in favor of the native Swift type properties).

Contributor guide

Tech stack
None
Domain
backend
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
stale
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
SwiftClang importerMacro handling
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70
Research direction
Investigate the ClangImporter source code in the Swift repository to understand how built in functions are currently recognized and imported. Look for existing handling of similar builtin * functions and determine the best approach to map the three macros (` builtin huge val`, ` builtin inf`, ` builtin nan`) to Swift's Double.infinity and Double.nan. Consider whether to import them as aliases or mark them unavailable in favor of the native Swift types. Check the relevant Swift evolution discussions or comments for any previous attempts.