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cgo: fix handling of signed enumerations

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Structs defined in C as containing a field with
an enum type are currently translated to Go as
a struct with an unsigned integer field, even if
some of the values contained in the enum are
negative.

This modification takes in consideration the values
defined in the enum, and conditionally defines the
Go type as signed if necessary.

The logic introduced was tested with gcc, which
will increase the type size if it contains both
negative numbers and values greater than 2^b/2-1,
and refuses to compile values which would be
problematic (2^64-1, but in fact the ISO C
restricts the range to the size of int).

R=rsc
CC=golang-dev
https://golang.org/cl/4119058
This commit is contained in:
Gustavo Niemeyer 2011-02-08 23:50:14 -05:00 committed by Russ Cox
parent 2aaabfc828
commit 4521782514
1 changed files with 23 additions and 9 deletions
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32
src/cmd/cgo/gcc.go
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@ -774,6 +774,8 @@ var dwarfToName = map[string]string{
"double complex": "complexdouble",
}
const signedDelta = 64
// Type returns a *Type with the same memory layout as
// dtype when used as the type of a variable or a struct field.
func (c *typeConv) Type(dtype dwarf.Type) *Type {
@ -839,7 +841,19 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
t.Align = 1
case *dwarf.EnumType:
switch t.Size {
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
t.C = "enum " + dt.EnumName
signed := 0
t.EnumValues = make(map[string]int64)
for _, ev := range dt.Val {
t.EnumValues[ev.Name] = ev.Val
if ev.Val < 0 {
signed = signedDelta
}
}
switch t.Size + int64(signed) {
default:
fatal("unexpected: %d-byte enum type - %s", t.Size, dtype)
case 1:
@ -850,14 +864,14 @@ func (c *typeConv) Type(dtype dwarf.Type) *Type {
t.Go = c.uint32
case 8:
t.Go = c.uint64
}
if t.Align = t.Size; t.Align >= c.ptrSize {
t.Align = c.ptrSize
}
t.C = "enum " + dt.EnumName
t.EnumValues = make(map[string]int64)
for _, ev := range dt.Val {
t.EnumValues[ev.Name] = ev.Val
case 1 + signedDelta:
t.Go = c.int8
case 2 + signedDelta:
t.Go = c.int16
case 4 + signedDelta:
t.Go = c.int32
case 8 + signedDelta:
t.Go = c.int64
}
case *dwarf.FloatType: