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cmd/ld: use count, not upper bound, in type of array

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DWARF says only one is necessary.
The count is preferable because it admits 0-length arrays.
Update debug/dwarf to handle either form.

LGTM=rsc
R=rsc
CC=golang-codereviews
https://golang.org/cl/111230044
This commit is contained in:
Rob Pike 2014-07-16 18:26:50 +00:00
parent 59af2c647b
commit 74c9cc8394
2 changed files with 15 additions and 8 deletions
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9
src/cmd/ld/dwarf.c
View File

@ -266,7 +266,7 @@ static struct DWAbbrev {
DW_TAG_subrange_type, DW_CHILDREN_no,
// No name!
DW_AT_type, DW_FORM_ref_addr,
DW_AT_upper_bound, DW_FORM_udata,
DW_AT_count, DW_FORM_udata,
0, 0
},
@ -992,7 +992,8 @@ defgotype(LSym *gotype)
s = decodetype_arrayelem(gotype);
newrefattr(die, DW_AT_type, defgotype(s));
fld = newdie(die, DW_ABRV_ARRAYRANGE, "range");
newattr(fld, DW_AT_upper_bound, DW_CLS_CONSTANT, decodetype_arraylen(gotype)-1, 0); // -1: want upper bound, not count.
// use actual length not upper bound; correct for 0-length arrays.
newattr(fld, DW_AT_count, DW_CLS_CONSTANT, decodetype_arraylen(gotype), 0);
newrefattr(fld, DW_AT_type, find_or_diag(&dwtypes, "uintptr"));
break;
@ -1256,7 +1257,7 @@ synthesizemaptypes(DWDie *die)
newattr(dwhk, DW_AT_byte_size, DW_CLS_CONSTANT, BucketSize * keysize, 0);
newrefattr(dwhk, DW_AT_type, indirect_key ? defptrto(keytype) : keytype);
fld = newdie(dwhk, DW_ABRV_ARRAYRANGE, "size");
newattr(fld, DW_AT_upper_bound, DW_CLS_CONSTANT, BucketSize, 0);
newattr(fld, DW_AT_count, DW_CLS_CONSTANT, BucketSize, 0);
newrefattr(fld, DW_AT_type, find_or_diag(&dwtypes, "uintptr"));
// Construct type to represent an array of BucketSize values
@ -1266,7 +1267,7 @@ synthesizemaptypes(DWDie *die)
newattr(dwhv, DW_AT_byte_size, DW_CLS_CONSTANT, BucketSize * valsize, 0);
newrefattr(dwhv, DW_AT_type, indirect_val ? defptrto(valtype) : valtype);
fld = newdie(dwhv, DW_ABRV_ARRAYRANGE, "size");
newattr(fld, DW_AT_upper_bound, DW_CLS_CONSTANT, BucketSize, 0);
newattr(fld, DW_AT_count, DW_CLS_CONSTANT, BucketSize, 0);
newrefattr(fld, DW_AT_type, find_or_diag(&dwtypes, "uintptr"));
// Construct bucket<K,V>

14
src/pkg/debug/dwarf/type.go
View File

@ -370,16 +370,22 @@ func (d *Data) readType(name string, r typeReader, off Offset, typeCache map[Off
// but haven't seen that in the wild yet.
switch kid.Tag {
case TagSubrangeType:
max, ok := kid.Val(AttrUpperBound).(int64)
count, ok := kid.Val(AttrCount).(int64)
if !ok {
max = -2 // Count == -1, as in x[].
// Old binaries may have an upper bound instead.
count, ok = kid.Val(AttrUpperBound).(int64)
if ok {
count++ // Length is one more than upper bound.
} else {
count = -1 // As in x[].
}
}
if ndim == 0 {
t.Count = max + 1
t.Count = count
} else {
// Multidimensional array.
// Create new array type underneath this one.
t.Type = &ArrayType{Type: t.Type, Count: max + 1}
t.Type = &ArrayType{Type: t.Type, Count: count}
}
ndim++
case TagEnumerationType: