cmd/cgo: roll back "use C exact-width integer types to represent Go types"

Roll back CL 159258 and CL 168337. Those changes broke existing
code. I can't see any way to keep existing code working while also
producing good error messages for types like C.ulong (such as the ones
already tested for in misc/cgo/errors).

This is not an exact roll back because parts of the code have changed
since those CLs.

Updates #29878
Fixes #31093

Change-Id: I56fe76c167ff0ab381ed273b9ca4b952402e1434
Reviewed-on: https://go-review.googlesource.com/c/go/+/180357
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

misc/cgo/test/cgo_test.go

@@ -56,7 +56,6 @@ func Test25143(t *testing.T)                 { test25143(t) }
 func Test26066(t *testing.T)                 { test26066(t) }
 func Test27660(t *testing.T)                 { test27660(t) }
 func Test28896(t *testing.T)                 { test28896(t) }
-func Test29878(t *testing.T)                 { test29878(t) }
 func Test30065(t *testing.T)                 { test30065(t) }
 func TestAlign(t *testing.T)                 { testAlign(t) }
 func TestAtol(t *testing.T)                  { testAtol(t) }

misc/cgo/test/test.go

@@ -849,10 +849,6 @@ static int f29748(S29748 *p) { return 0; }
 static void issue29781F(char **p, int n) {}
 #define ISSUE29781C 0
 
-// issue 29878
-uint64_t issue29878exported(int8_t);  // prototype must match
-int16_t issue29878function(uint32_t arg) { return issue29878exported(arg); }
-
 */
 import "C"
 
@@ -2054,14 +2050,6 @@ func issue29781G() {
 		X))
 }
 
-func test29878(t *testing.T) {
-	const arg uint32 = 123                    // fits into all integer types
-	var ret int16 = C.issue29878function(arg) // no conversions needed
-	if int64(ret) != int64(arg) {
-		t.Errorf("return value unexpected: got %d, want %d", ret, arg)
-	}
-}
-
 // issue 30065
 
 func test30065(t *testing.T) {

misc/cgo/test/testx.go

@@ -535,8 +535,3 @@ func test20910(t *testing.T) {
 // issue 28772 part 2
 
 const issue28772Constant2 = C.issue28772Constant2
-
-//export issue29878exported
-func issue29878exported(arg int8) uint64 {
-	return uint64(arg)
-}

src/cmd/cgo/doc.go

@@ -148,8 +148,6 @@ C.long, C.ulong (unsigned long), C.longlong (long long),
 C.ulonglong (unsigned long long), C.float, C.double,
 C.complexfloat (complex float), and C.complexdouble (complex double).
 The C type void* is represented by Go's unsafe.Pointer.
-The C sized integer types (int8_t, uint8_t, …) are represented by their Go
-counterparts (int8, uint8, …).
 The C types __int128_t and __uint128_t are represented by [16]byte.
 
 A few special C types which would normally be represented by a pointer
@@ -298,7 +296,7 @@ Go functions can be exported for use by C code in the following way:
 
 They will be available in the C code as:
 
-	extern int64_t MyFunction(int arg1, int arg2, GoString arg3);
+	extern GoInt64 MyFunction(int arg1, int arg2, GoString arg3);
 	extern struct MyFunction2_return MyFunction2(int arg1, int arg2, GoString arg3);
 
 found in the _cgo_export.h generated header, after any preambles

src/cmd/cgo/gcc.go

@@ -23,7 +23,6 @@ import (
 	"internal/xcoff"
 	"math"
 	"os"
-	"regexp"
 	"strconv"
 	"strings"
 	"unicode"
@@ -2047,8 +2046,6 @@ type typeConv struct {
 
 	ptrSize int64
 	intSize int64
-
-	exactWidthIntegerTypes map[string]*Type
 }
 
 var tagGen int
@@ -2091,21 +2088,6 @@ func (c *typeConv) Init(ptrSize, intSize int64) {
 	} else {
 		c.goVoidPtr = c.Ident("unsafe.Pointer")
 	}
-
-	c.exactWidthIntegerTypes = make(map[string]*Type)
-	for _, t := range []ast.Expr{
-		c.int8, c.int16, c.int32, c.int64,
-		c.uint8, c.uint16, c.uint32, c.uint64,
-	} {
-		name := t.(*ast.Ident).Name
-		u := new(Type)
-		*u = *goTypes[name]
-		if u.Align > ptrSize {
-			u.Align = ptrSize
-		}
-		u.Go = t
-		c.exactWidthIntegerTypes[name] = u
-	}
 }
 
 // base strips away qualifiers and typedefs to get the underlying type
@@ -2477,26 +2459,6 @@ func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
 			t.Align = c.ptrSize
 			break
 		}
-		// Exact-width integer types.  These are always compatible with
-		// the corresponding Go types since the C standard requires
-		// them to have no padding bit and use the two’s complement
-		// representation.
-		if exactWidthIntegerType.MatchString(dt.Name) {
-			sub := c.Type(dt.Type, pos)
-			goname := strings.TrimPrefix(dt.Name, "__")
-			goname = strings.TrimSuffix(goname, "_t")
-			u := c.exactWidthIntegerTypes[goname]
-			if sub.Size != u.Size {
-				fatalf("%s: unexpected size: %d vs. %d – %s", lineno(pos), sub.Size, u.Size, dtype)
-			}
-			if sub.Align != u.Align {
-				fatalf("%s: unexpected alignment: %d vs. %d – %s", lineno(pos), sub.Align, u.Align, dtype)
-			}
-			t.Size = u.Size
-			t.Align = u.Align
-			t.Go = u.Go
-			break
-		}
 		name := c.Ident("_Ctype_" + dt.Name)
 		goIdent[name.Name] = name
 		sub := c.Type(dt.Type, pos)
@@ -2632,8 +2594,6 @@ func (c *typeConv) Type(dtype dwarf.Type, pos token.Pos) *Type {
 	return t
 }
 
-var exactWidthIntegerType = regexp.MustCompile(`^(__)?u?int(8|16|32|64)_t$`)
-
 // isStructUnionClass reports whether the type described by the Go syntax x
 // is a struct, union, or class with a tag.
 func isStructUnionClass(x ast.Expr) bool {

src/cmd/cgo/out.go

@@ -1367,19 +1367,19 @@ func c(repr string, args ...interface{}) *TypeRepr {
 
 // Map predeclared Go types to Type.
 var goTypes = map[string]*Type{
-	"bool":       {Size: 1, Align: 1, C: c("uint8_t")},
-	"byte":       {Size: 1, Align: 1, C: c("uint8_t")},
+	"bool":       {Size: 1, Align: 1, C: c("GoUint8")},
+	"byte":       {Size: 1, Align: 1, C: c("GoUint8")},
 	"int":        {Size: 0, Align: 0, C: c("GoInt")},
 	"uint":       {Size: 0, Align: 0, C: c("GoUint")},
-	"rune":       {Size: 4, Align: 4, C: c("int32_t")},
-	"int8":       {Size: 1, Align: 1, C: c("int8_t")},
-	"uint8":      {Size: 1, Align: 1, C: c("uint8_t")},
-	"int16":      {Size: 2, Align: 2, C: c("int16_t")},
-	"uint16":     {Size: 2, Align: 2, C: c("uint16_t")},
-	"int32":      {Size: 4, Align: 4, C: c("int32_t")},
-	"uint32":     {Size: 4, Align: 4, C: c("uint32_t")},
-	"int64":      {Size: 8, Align: 8, C: c("int64_t")},
-	"uint64":     {Size: 8, Align: 8, C: c("uint64_t")},
+	"rune":       {Size: 4, Align: 4, C: c("GoInt32")},
+	"int8":       {Size: 1, Align: 1, C: c("GoInt8")},
+	"uint8":      {Size: 1, Align: 1, C: c("GoUint8")},
+	"int16":      {Size: 2, Align: 2, C: c("GoInt16")},
+	"uint16":     {Size: 2, Align: 2, C: c("GoUint16")},
+	"int32":      {Size: 4, Align: 4, C: c("GoInt32")},
+	"uint32":     {Size: 4, Align: 4, C: c("GoUint32")},
+	"int64":      {Size: 8, Align: 8, C: c("GoInt64")},
+	"uint64":     {Size: 8, Align: 8, C: c("GoUint64")},
 	"float32":    {Size: 4, Align: 4, C: c("GoFloat32")},
 	"float64":    {Size: 8, Align: 8, C: c("GoFloat64")},
 	"complex64":  {Size: 8, Align: 4, C: c("GoComplex64")},
@@ -1871,10 +1871,16 @@ const gccExportHeaderProlog = `
 #ifndef GO_CGO_PROLOGUE_H
 #define GO_CGO_PROLOGUE_H
 
-#include <stdint.h>
-
-typedef intGOINTBITS_t GoInt;
-typedef uintGOINTBITS_t GoUint;
+typedef signed char GoInt8;
+typedef unsigned char GoUint8;
+typedef short GoInt16;
+typedef unsigned short GoUint16;
+typedef int GoInt32;
+typedef unsigned int GoUint32;
+typedef long long GoInt64;
+typedef unsigned long long GoUint64;
+typedef GoIntGOINTBITS GoInt;
+typedef GoUintGOINTBITS GoUint;
 typedef __SIZE_TYPE__ GoUintptr;
 typedef float GoFloat32;
 typedef double GoFloat64;