From 12e5efd71011fbb5816a1d815e91b5c865fa9a83 Mon Sep 17 00:00:00 2001 From: Mark Ryan Date: Fri, 25 Apr 2025 17:23:49 +0200 Subject: [PATCH] cmd/link: fix cgo on riscv64 when building with gcc-15 It's not currently possible to build cgo programs that are partially compiled with gcc-15 on riscv64 using the internal linker. There are two reasons for this. 1. When gcc-15 compiles _cgo_export.c, which contains no actual code, for a riscv64 target, it emits a label in the .text section called .Letext0. This label is referred to by another section, .debug_line, and an entry is generated in the symbol table for it. The Go linker panics when processing the .Letext0 symbol in _cgo_export.o, as it occurs in an empty section. 2. GCC-15 is generating additional debug symbols with the .LVUS prefix, e.g., .LVUS33, that need to be ignored. We fix the issue by removing the check in cmd/link/internal/loader/loader.go that panics if we encounter a symbol in an empty section (the comments preceding this check suggest it's safe to remove it) and by adding .LVUS to the list of symbol prefixes to ignore. Fixes #72840 Change-Id: I00658b6bdd01606dde1581b5bc2f42edfc37de82 Reviewed-on: https://go-review.googlesource.com/c/go/+/668276 Auto-Submit: Dmitri Shuralyov LUCI-TryBot-Result: Go LUCI Reviewed-by: Dmitri Shuralyov Reviewed-by: Joel Sing Reviewed-by: Carlos Amedee Reviewed-by: Meng Zhuo --- src/cmd/link/internal/loadelf/ldelf.go | 2 +- src/cmd/link/internal/loader/loader.go | 8 -------- 2 files changed, 1 insertion(+), 9 deletions(-) diff --git a/src/cmd/link/internal/loadelf/ldelf.go b/src/cmd/link/internal/loadelf/ldelf.go index e0363b5535..9f251e746b 100644 --- a/src/cmd/link/internal/loadelf/ldelf.go +++ b/src/cmd/link/internal/loadelf/ldelf.go @@ -609,7 +609,7 @@ func Load(l *loader.Loader, arch *sys.Arch, localSymVersion int, f *bio.Reader, continue } - if strings.HasPrefix(elfsym.name, ".LASF") || strings.HasPrefix(elfsym.name, ".LLRL") || strings.HasPrefix(elfsym.name, ".LLST") { + if strings.HasPrefix(elfsym.name, ".LASF") || strings.HasPrefix(elfsym.name, ".LLRL") || strings.HasPrefix(elfsym.name, ".LLST") || strings.HasPrefix(elfsym.name, ".LVUS") { // gcc on s390x and riscv64 does this. continue } diff --git a/src/cmd/link/internal/loader/loader.go b/src/cmd/link/internal/loader/loader.go index 6a7057b80e..128173b8cf 100644 --- a/src/cmd/link/internal/loader/loader.go +++ b/src/cmd/link/internal/loader/loader.go @@ -1719,14 +1719,6 @@ func (l *Loader) GetVarDwarfAuxSym(i Sym) Sym { // expected to have the actual content/payload) and then a set of // interior loader.Sym's that point into a portion of the container. func (l *Loader) AddInteriorSym(container Sym, interior Sym) { - // Container symbols are expected to have content/data. - // NB: this restriction may turn out to be too strict (it's possible - // to imagine a zero-sized container with an interior symbol pointing - // into it); it's ok to relax or remove it if we counter an - // oddball host object that triggers this. - if l.SymSize(container) == 0 && len(l.Data(container)) == 0 { - panic("unexpected empty container symbol") - } // The interior symbols for a container are not expected to have // content/data or relocations. if len(l.Data(interior)) != 0 {