OpenSoftLinking

An open-source reimplementation of Apple's private SoftLinking.framework (internally tagged SoftLinking-71 on macOS 26.4), plus the full WebKit-derived SOFT_LINK_* macro suite re-prefixed OPEN_SOFT_LINK_*.

What it does

Loads Apple frameworks at runtime with fallback paths and Catalyst-aware path resolution (delegated to dyld via dlopen_from). Provides macros to soft-link frameworks, classes, functions, pointers, constants, and variables the same way UIKit, AVFoundation, and WebKit do internally.

Requirements

• Swift Package Manager (swift-tools 6.3+)
• macOS 10.15+ / iOS 13+ / tvOS 13+ / watchOS 6+ / visionOS 1+ / Mac Catalyst 13+

Installation

dependencies: [
    .package(url: "https://github.com/<owner>/OpenSoftLinking", from: "0.1.0"),
]

In a C / Objective-C source file:

#import <OpenSoftLinking/OpenSoftLinking.h>

OPEN_SOFT_LINK_FRAMEWORK(UIKit)
OPEN_SOFT_LINK_CLASS(UIKit, UIApplication)
OPEN_SOFT_LINK_POINTER(UIKit, UIApp, UIApplication *)

// Later…
Class appClass = getUIApplicationClass();

Swift consumers bridge via a bridging header:

// MyBridgingHeader.h
#import <OpenSoftLinking/OpenSoftLinking.h>
OPEN_SOFT_LINK_FRAMEWORK(UIKit)

Runtime API

void *_osl_dlopen(const char *const *paths, char **errorMessage);
void *_osl_dlopen_audited(const char *const *paths);

paths is a NULL-terminated array of candidate framework paths. On success, returns the dyld handle of the first successful load. On failure with errorMessage non-NULL, writes a \n-joined string of per-path dlerror() messages that the caller must free().

Relation to Apple's SoftLinking

Aspect	Apple SoftLinking.framework	OpenSoftLinking
Symbol names	_sl_dlopen, _sl_dlopen_audited	_osl_dlopen, _osl_dlopen_audited
Macro names	N/A (internal)	OPEN_SOFT_LINK_*
dlopen flags	RTLD_LAZY | RTLD_FIRST	Same
Caller-aware dyld lookup	Via dlopen_from + LR	Same
Catalyst path resolution	Delegated to dyld	Same
Error aggregation	\n-joined strings + os_log_info	Same
License	Proprietary	LGPL-2.1

License

LGPL-2.1. The SoftLinking.h macro suite is derived from WebKit's Source/WTF/wtf/cocoa/SoftLinking.h (LGPL-2.1). See LICENSE.

Known limitations

• calloc failure on the slow-path (error aggregation) triggers abort(), matching Apple's __assert_rtn behavior; not unit tested.
• dlopen_from is a stable SPI since macOS 10.15 / iOS 13; no formal guarantee against future removal.
• Byte-equivalent parity with Apple's SoftLinking binary is not a goal — only behavioral parity.