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ssa: fix zero-value map indexing #1835

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Merged
xushiwei merged 5 commits into from
Apr 28, 2026
Merged

ssa: fix zero-value map indexing #1835

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9b9311f
ssa: fix zero-value map indexing
zhouguangyuan0718 Apr 27, 2026
2ed8dcb
Apply suggestion from @gemini-code-assist[bot]
zhouguangyuan0718 Apr 28, 2026
029b653
Format CHECK directive in in.go
zhouguangyuan0718 Apr 28, 2026
a92a668
Fix comment formatting in in.go
zhouguangyuan0718 Apr 28, 2026
313211f
Merge branch 'goplus:main' into main-fix-zerovalue
zhouguangyuan0718 Apr 28, 2026
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1 change: 1 addition & 0 deletions cl/_testlibgo/mapzero/expect.txt
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
runtime error: index out of range
16 changes: 16 additions & 0 deletions cl/_testlibgo/mapzero/in.go
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@@ -0,0 +1,16 @@
// LITTEST
package main

import "fmt"

var a = 0

func main() {
defer func() {
err := recover()
fmt.Println(err)
}()
// CHECK: call ptr @"github.com/goplus/llgo/runtime/internal/runtime.MapAccess1"(ptr @"map[_llgo_int]_llgo_int", ptr null, ptr {{%.*}})
m := [0]map[int]int{}[a][0]
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@fennoai fennoai Bot Apr 27, 2026

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Nit (readability): This expression is dense and tests two things at once (array bounds check + nil map representation). A short comment would help future readers:

// Index a zero-length array literal to get a nil map, then index that nil map.
// The array index panics with "index out of range" before the map access.

print(m)
}
3 changes: 0 additions & 3 deletions ssa/datastruct.go
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Expand Up @@ -284,9 +284,6 @@ func (b Builder) Index(x, idx Expr, takeAddr func() (addr Expr, zero bool)) Expr
return prog.Zero(telem)
}
if ptr.IsNil() {
if x.impl.IsConstant() {
return Expr{llvm.ConstExtractElement(x.impl, idx.impl), telem}
}
ptr = b.Alloc(x.Type, false)
b.impl.CreateStore(x.impl, ptr.impl)
}
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2 changes: 1 addition & 1 deletion ssa/expr.go
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Expand Up @@ -163,7 +163,7 @@ func (p Program) Zero(t Type) Expr {
}
ret = p.Zero(p.rtType(name)).impl
case *types.Map:
ret = p.Zero(p.rtType("Map")).impl
ret = p.Zero(p.Pointer(p.rtType("Map"))).impl
case *types.Tuple:
n := u.Len()
flds := make([]llvm.Value, n)
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