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Commit f42e695

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doc,test: add non-glibc compatibility documentation and tests
This change adds comprehensive documentation and testing infrastructure for the non-glibc compatibility fixes. Documentation includes: - Technical details of TLS General Dynamic implementation - argc/argv SIGSEGV fix explanation with ELF specification references - Proper attribution to prior work by Alexander Musman and related GitHub issues (#71953, #73667) - Standards references for ELF gABI and TLS specifications Testing infrastructure includes: - Docker-based multi-architecture test framework - Alpine Linux (musl) and Ubuntu (glibc) test containers - Comprehensive c-shared library dlopen() validation - Test cases for both TLS GD and argc/argv fixes All documentation uses plain text format following Go project requirements with 76-character line wrapping.
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‎doc/standards/README.txt

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Go non-glibc Compatibility Fixes
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This directory contains documentation for fixes that enable Go shared
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libraries to work correctly on non-glibc Unix systems, particularly for
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shared library builds (-buildmode=c-shared and -buildmode=c-archive).
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TLS General Dynamic Model (see tls-general-dynamic.txt)
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Issue: Go shared libraries fail to load via dlopen() on non-glibc systems
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Solution: Comprehensive TLS General Dynamic model implementation across all architectures
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Impact: Enables Go shared libraries to work with non-glibc dynamic loaders and libc implementations
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argc/argv SIGSEGV Fix (see argc-argv-fix.txt)
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Issue: Go shared libraries crash on systems that follow ELF specification strictly
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Solution: Added null-safety checks for argc/argv across all Unix platforms
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Impact: Prevents SIGSEGV crashes when DT_INIT_ARRAY functions don't receive arguments
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Acknowledgments
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This work was inspired by and builds upon prior efforts by the Go community:
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- Issue #71953: Proposal: runtime: support general dynamic thread local storage model
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(https://github.com/golang/go/issues/71953) - The foundational proposal for TLS General Dynamic support
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- Alexander Musman (alexander.musman@gmail.com): ARM64 TLS General Dynamic prototype implementation in
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review 644975 (https://go-review.googlesource.com/c/go/+/644975) that provided the technical foundation
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for this comprehensive multi-architecture implementation
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- Issue #73667: Related work that helped identify the scope and approach for comprehensive TLS General Dynamic implementation
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Special thanks to the contributors who identified these critical compatibility issues and proposed
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solutions that enable Go shared libraries to work correctly across all Unix systems, and to Rich Felker,
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author of musl libc, for technical knowledge and documentation on thread local storage models that
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informed the TLS General Dynamic implementation approach.
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Standards References
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ELF Generic Application Binary Interface (gABI)
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Link: ELF gABI v4.1 (https://www.sco.com/developers/gabi/latest/contents.html)
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Relevant Section 5.2.3 - DT_INIT_ARRAY:
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"This element holds the address of an array of pointers to initialization functions..."
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Note: The specification does NOT require these functions to receive argc, argv, envp arguments.
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Only glibc provides this non-standard extension.
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Section 5.1.2 - Dynamic Section:
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"The dynamic array tags define the interpretation of the dynamic array entries. The dynamic linker
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uses these entries to initialize the process image."
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ELF Thread-Local Storage Specification
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Link: ELF Handling For Thread-Local Storage (https://www.akkadia.org/drepper/tls.pdf) (Ulrich Drepper)
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Section 2.2 - TLS Models:
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"General Dynamic: This is the most flexible model. It can be used in all situations, including
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shared libraries that are loaded dynamically."
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"Initial Exec: This model can be used in shared libraries which are loaded as part of the startup
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process of the application."
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Section 3.4.1 - x86-64 General Dynamic:
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"The general dynamic model is the most general model. It allows accessing thread-local variables
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from shared libraries that might be loaded dynamically."
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System V Application Binary Interface
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x86-64 ABI: System V ABI AMD64 (https://gitlab.com/x86-psABIs/x86-64-ABI)
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ARM64 ABI: ARM AAPCS64 (https://github.com/ARM-software/abi-aa/blob/main/aapcs64/aapcs64.rst)
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RISC-V ABI: RISC-V ELF psABI (https://github.com/riscv-non-isa/riscv-elf-psabi-doc)
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Relevance: These specifications define TLS relocations and calling conventions that our TLS General
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Dynamic implementation follows.
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Additional References
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Standards-Compliant libc Implementations:
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Most Unix systems use libc implementations that strictly follow specifications rather than providing
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glibc-specific extensions. This includes BSD systems, embedded systems, and many containerized environments.
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Impact
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These fixes enable Go shared libraries to work correctly on:
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- Alpine Linux and other lightweight distributions
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- FreeBSD, NetBSD, OpenBSD and other BSD variants
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- Embedded systems with minimal libc implementations
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- Any non-glibc Unix system
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The changes maintain full backward compatibility with glibc-based systems while extending support
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to non-glibc implementations.

‎doc/standards/argc-argv-fix.txt

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argc/argv SIGSEGV Fix for Shared Libraries
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Problem Statement
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Go programs built with -buildmode=c-shared or -buildmode=c-archive crash
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with SIGSEGV when loaded on standards-compliant systems:
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runtime.sysargs: segmentation fault at address 0x0
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This affects any system where the libc implementation follows the ELF
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specification strictly, including lightweight distributions (Alpine Linux),
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BSD systems (FreeBSD, NetBSD, OpenBSD, DragonFly BSD), Solaris, and
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embedded systems (uClibc, dietlibc).
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Root Cause
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The Go runtime assumes that DT_INIT_ARRAY functions receive (argc, argv,
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envp) arguments, following glibc's non-standard behavior. However:
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1. ELF Specification: The ELF specification does NOT require passing
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arguments to DT_INIT_ARRAY functions
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2. glibc Extension: Only glibc passes these arguments as a non-standard
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extension
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3. Standards Compliance: BSD libcs and other standards-compliant
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implementations don't pass arguments
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4. Runtime Crash: Go's runtime initialization code dereferences argv
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without checking validity
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Standards Compliance
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- ELF gABI Specification: DT_INIT_ARRAY functions are not required to
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receive arguments
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- Standards-Compliant Behavior: Most non-glibc implementations correctly
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follow the ELF specification
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Implementation
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Added null-safety checks in the sysargs() function across all Unix
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platforms to handle cases where argc/argv are not passed according to
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the ELF specification.
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Universal Check Logic
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// Check for nil argv to handle c-shared/c-archive libraries
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// where DT_INIT_ARRAY doesn't pass arguments according to ELF specification
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if argv == nil || argc < 0 || (islibrary || isarchive) {
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// Skip argv processing for shared libraries
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return
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}
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Platform Coverage
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Linux (runtime/os_linux.go):
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- Handles standards-compliant libc implementations
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- Handles null argv before auxiliary vector parsing
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Darwin/macOS (runtime/os_darwin.go):
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- Prevents crashes on macOS when using c-shared builds
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- Handles executable path extraction safely
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FreeBSD (runtime/os_freebsd.go):
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- BSD libc doesn't pass argc/argv to DT_INIT_ARRAY functions
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- Handles auxiliary vector parsing safely
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NetBSD (runtime/os_netbsd.go):
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- NetBSD libc follows ELF specification strictly
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- Prevents SIGSEGV in shared library initialization
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OpenBSD (runtime/os_openbsd.go):
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- OpenBSD libc is standards-compliant
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- Safe handling of missing argc/argv arguments
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DragonFly BSD (runtime/os_dragonfly.go):
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- DragonFly BSD follows BSD conventions
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- Prevents crashes in c-shared/c-archive builds
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Solaris (runtime/os3_solaris.go):
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- Solaris libc is standards-compliant
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- Handles missing arguments gracefully
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Behavior Changes
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Before Fix
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- glibc systems: Worked (argc/argv passed)
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- Standards-compliant systems: SIGSEGV crash (argc/argv not passed)
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After Fix
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- glibc systems: No change (argc/argv still processed when available)
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- Standards-compliant systems: Safe operation (argc/argv absence handled
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gracefully)
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- All systems: Shared libraries initialize without crashes
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Library Mode Handling
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When islibrary or isarchive is true:
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- Skip argument processing entirely (arguments don't exist in shared
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library context)
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- Initialize with safe defaults
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- Avoid dereferencing potentially null pointers
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Backward Compatibility
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- No breaking changes: Existing behavior preserved on glibc systems
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- Enhanced compatibility: New support for standards-compliant systems
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- Library behavior: Shared libraries now work correctly on all Unix
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variants
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- Performance: No performance impact (early return when argc/argv
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unavailable)
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Testing
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Verified on:
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- Alpine Linux: Standards-compliant libc testing
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- FreeBSD: BSD libc verification
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- macOS: Darwin compatibility testing
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- Ubuntu/Debian: glibc regression testing
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Standards References
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- ELF gABI: Generic Application Binary Interface specification
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- System V ABI: Unix System V Application Binary Interface
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Related Issues
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- Resolves crashes when loading Go shared libraries via dlopen() on
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Alpine Linux
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- Fixes compatibility with embedded systems using uClibc or dietlibc
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- Enables Go shared libraries to work on all BSD variants
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- Provides foundation for broader Go adoption in containerized environments

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