link.go

     1  // Copyright 2021 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package base
     6  
     7  import (
     8  	"cmd/internal/obj"
     9  )
    10  
    11  // ReservedImports are import paths used internally for generated
    12  // symbols by the compiler.
    13  //
    14  // The linker uses the magic symbol prefixes "go:" and "type:".
    15  // Avoid potential confusion between import paths and symbols
    16  // by rejecting these reserved imports for now. Also, people
    17  // "can do weird things in GOPATH and we'd prefer they didn't
    18  // do _that_ weird thing" (per rsc). See also #4257.
    19  var ReservedImports = map[string]bool{
    20  	"go":   true,
    21  	"type": true,
    22  }
    23  
    24  var Ctxt *obj.Link
    25  
    26  // TODO(mdempsky): These should probably be obj.Link methods.
    27  
    28  // PkgLinksym returns the linker symbol for name within the given
    29  // package prefix. For user packages, prefix should be the package
    30  // path encoded with objabi.PathToPrefix.
    31  func PkgLinksym(prefix, name string, abi obj.ABI) *obj.LSym {
    32  	if name == "_" {
    33  		// TODO(mdempsky): Cleanup callers and Fatalf instead.
    34  		return linksym(prefix, "_", abi)
    35  	}
    36  	sep := "."
    37  	if ReservedImports[prefix] {
    38  		sep = ":"
    39  	}
    40  	return linksym(prefix, prefix+sep+name, abi)
    41  }
    42  
    43  // Linkname returns the linker symbol for the given name as it might
    44  // appear within a //go:linkname directive.
    45  func Linkname(name string, abi obj.ABI) *obj.LSym {
    46  	return linksym("_", name, abi)
    47  }
    48  
    49  // linksym is an internal helper function for implementing the above
    50  // exported APIs.
    51  func linksym(pkg, name string, abi obj.ABI) *obj.LSym {
    52  	return Ctxt.LookupABIInit(name, abi, func(r *obj.LSym) { r.Pkg = pkg })
    53  }
    54
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