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Add a stub of __context__ builtin from kernel's sparse #208

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Add a stub of __context__ builtin from kernel's sparse #208

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10 changes: 10 additions & 0 deletions src/frontc/cabs2cil.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -4423,11 +4423,21 @@ and doExp (asconst: bool) (* This expression is used as a constant *)
| Lval (Var {vname= ("__builtin_nan" | "__builtin_nanf" | "__builtin_nanl" | "__builtin_nans" | "__builtin_nansf" | "__builtin_nansl"); _}, NoOffset) -> true
| _ -> false
in
let isSparseBuiltin =
match f'' with
| Lval (Var {vname= ("__context__"); _}, NoOffset) ->
ignore (warn "Ignoring __context__ builtin of Linux kernel Sparse");
true
| _ -> false
in
if isBuiltinNan && asconst then
(* Replace call to builtin nan with computation yielding NaN *)
let onef = Const(CReal(0.0,FDouble,None)) in
let zerodivzero = mkCast ~kind:Internal ~e:(BinOp(Div,onef,onef,doubleType)) ~newt:resType in
(empty,zerodivzero,resType)
else if isSparseBuiltin then
let one = Const(CInt(cilint_of_int 1, IInt, None)) in
(empty, one, intType)
Comment on lines +4438 to +4440
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@sim642 sim642 Jan 14, 2026

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Is it really necessary to replace it with an arbitrary constant 1?
Why does it need to be handled in CIL? Couldn't it just remain as a normal function call that's added to Goblint's LibraryFunctions?

Or alternatively, wouldn't it be enough to introduce initSparseBuiltins like

cil/src/cil.ml

Line 2903 in e21285a

let initGccBuiltins () : unit =
if it needs an implicit declaration and a signature?
Most builtins are not specifically handled here, only the ones that really have to do something at compile time. But this __context__ doesn't seem to require anything like this.

else (
(* If the "--forceRLArgEval" flag was used, make sure
we evaluate args right-to-left.
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4 changes: 4 additions & 0 deletions test/small1/sparse_context.c
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@@ -0,0 +1,4 @@
void test() {
__context__(RCU);
__context__(This, should, be, ignored);
}