sym.go

     1  // Copyright 2017 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 types
     6  
     7  import (
     8  	"cmd/compile/internal/base"
     9  	"cmd/internal/obj"
    10  	"unicode"
    11  	"unicode/utf8"
    12  )
    13  
    14  // Sym represents an object name in a segmented (pkg, name) namespace.
    15  // Most commonly, this is a Go identifier naming an object declared within a package,
    16  // but Syms are also used to name internal synthesized objects.
    17  //
    18  // As an exception, field and method names that are exported use the Sym
    19  // associated with localpkg instead of the package that declared them. This
    20  // allows using Sym pointer equality to test for Go identifier uniqueness when
    21  // handling selector expressions.
    22  //
    23  // Ideally, Sym should be used for representing Go language constructs,
    24  // while cmd/internal/obj.LSym is used for representing emitted artifacts.
    25  //
    26  // NOTE: In practice, things can be messier than the description above
    27  // for various reasons (historical, convenience).
    28  type Sym struct {
    29  	Linkname string // link name
    30  
    31  	Pkg  *Pkg
    32  	Name string // object name
    33  
    34  	// The unique ONAME, OTYPE, OPACK, or OLITERAL node that this symbol is
    35  	// bound to within the current scope. (Most parts of the compiler should
    36  	// prefer passing the Node directly, rather than relying on this field.)
    37  	//
    38  	// Deprecated: New code should avoid depending on Sym.Def. Add
    39  	// mdempsky@ as a reviewer for any CLs involving Sym.Def.
    40  	Def Object
    41  
    42  	flags bitset8
    43  }
    44  
    45  const (
    46  	symOnExportList = 1 << iota // added to exportlist (no need to add again)
    47  	symUniq
    48  	symSiggen // type symbol has been generated
    49  	symAsm    // on asmlist, for writing to -asmhdr
    50  	symFunc   // function symbol
    51  )
    52  
    53  func (sym *Sym) OnExportList() bool { return sym.flags&symOnExportList != 0 }
    54  func (sym *Sym) Uniq() bool         { return sym.flags&symUniq != 0 }
    55  func (sym *Sym) Siggen() bool       { return sym.flags&symSiggen != 0 }
    56  func (sym *Sym) Asm() bool          { return sym.flags&symAsm != 0 }
    57  func (sym *Sym) Func() bool         { return sym.flags&symFunc != 0 }
    58  
    59  func (sym *Sym) SetOnExportList(b bool) { sym.flags.set(symOnExportList, b) }
    60  func (sym *Sym) SetUniq(b bool)         { sym.flags.set(symUniq, b) }
    61  func (sym *Sym) SetSiggen(b bool)       { sym.flags.set(symSiggen, b) }
    62  func (sym *Sym) SetAsm(b bool)          { sym.flags.set(symAsm, b) }
    63  func (sym *Sym) SetFunc(b bool)         { sym.flags.set(symFunc, b) }
    64  
    65  func (sym *Sym) IsBlank() bool {
    66  	return sym != nil && sym.Name == "_"
    67  }
    68  
    69  // Deprecated: This method should not be used directly. Instead, use a
    70  // higher-level abstraction that directly returns the linker symbol
    71  // for a named object. For example, reflectdata.TypeLinksym(t) instead
    72  // of reflectdata.TypeSym(t).Linksym().
    73  func (sym *Sym) Linksym() *obj.LSym {
    74  	abi := obj.ABI0
    75  	if sym.Func() {
    76  		abi = obj.ABIInternal
    77  	}
    78  	return sym.LinksymABI(abi)
    79  }
    80  
    81  // Deprecated: This method should not be used directly. Instead, use a
    82  // higher-level abstraction that directly returns the linker symbol
    83  // for a named object. For example, (*ir.Name).LinksymABI(abi) instead
    84  // of (*ir.Name).Sym().LinksymABI(abi).
    85  func (sym *Sym) LinksymABI(abi obj.ABI) *obj.LSym {
    86  	if sym == nil {
    87  		base.Fatalf("nil symbol")
    88  	}
    89  	if sym.Linkname != "" {
    90  		return base.Linkname(sym.Linkname, abi)
    91  	}
    92  	return base.PkgLinksym(sym.Pkg.Prefix, sym.Name, abi)
    93  }
    94  
    95  // Less reports whether symbol a is ordered before symbol b.
    96  //
    97  // Symbols are ordered exported before non-exported, then by name, and
    98  // finally (for non-exported symbols) by package path.
    99  func (a *Sym) Less(b *Sym) bool {
   100  	if a == b {
   101  		return false
   102  	}
   103  
   104  	// Nil before non-nil.
   105  	if a == nil {
   106  		return true
   107  	}
   108  	if b == nil {
   109  		return false
   110  	}
   111  
   112  	// Exported symbols before non-exported.
   113  	ea := IsExported(a.Name)
   114  	eb := IsExported(b.Name)
   115  	if ea != eb {
   116  		return ea
   117  	}
   118  
   119  	// Order by name and then (for non-exported names) by package
   120  	// height and path.
   121  	if a.Name != b.Name {
   122  		return a.Name < b.Name
   123  	}
   124  	if !ea {
   125  		return a.Pkg.Path < b.Pkg.Path
   126  	}
   127  	return false
   128  }
   129  
   130  // IsExported reports whether name is an exported Go symbol (that is,
   131  // whether it begins with an upper-case letter).
   132  func IsExported(name string) bool {
   133  	if r := name[0]; r < utf8.RuneSelf {
   134  		return 'A' <= r && r <= 'Z'
   135  	}
   136  	r, _ := utf8.DecodeRuneInString(name)
   137  	return unicode.IsUpper(r)
   138  }
   139
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