cmd/link/internal/loadpe: handle _main reference properly

When building CGO internal linking on windows 386, make sure to avoid
rewriting references to "_main" to "main" when reading symbols during
host object loading; the main routine defined by the Go runtime is
still named "_main" (not "main"). If we don't do this, we wind up with
an SXREF symbol named "main", which can then cause the loader to pull
an actual "main" symbol out of a host archive, which is undesirable.

Updates #35006.

Change-Id: I3768e3617b560552f4522e9e72af879c6adf7705
Reviewed-on: https://go-review.googlesource.com/c/go/+/410124
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Auto-Submit: Than McIntosh <thanm@google.com>
Run-TryBot: Than McIntosh <thanm@google.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>

diff --git a/src/cmd/link/internal/loadpe/ldpe.go b/src/cmd/link/internal/loadpe/ldpe.go
index bfe2e837c9bc71d0fbb31f13e9a4b10a599c03e0..bc66252cfad37c10d4acade4138d48813799ec53 100644 (file)
--- a/src/cmd/link/internal/loadpe/ldpe.go
+++ b/src/cmd/link/internal/loadpe/ldpe.go
@@ -551,7 +551,13 @@ func (state *peLoaderState) readpesym(pesym *pe.COFFSymbol) (*loader.SymbolBuild
                                name = strings.TrimPrefix(name, "__imp_") // __imp_Name => Name
                        }
                }
-               if state.arch.Family == sys.I386 && name[0] == '_' {
+               // A note on the "_main" exclusion below: the main routine
+               // defined by the Go runtime is named "_main", not "main", so
+               // when reading references to _main from a host object we want
+               // to avoid rewriting "_main" to "main" in this specific
+               // instance. See #issuecomment-1143698749 on #35006 for more
+               // details on this problem.
+               if state.arch.Family == sys.I386 && name[0] == '_' && name != "_main" {
                        name = name[1:] // _Name => Name
                }
        }