support c-variadic functions in rustc_const_eval
#150601
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -5,6 +5,7 @@ use std::borrow::Cow; | |
| use either::{Left, Right}; | ||
| use rustc_abi::{self as abi, ExternAbi, FieldIdx, Integer, VariantIdx}; | ||
| use rustc_data_structures::assert_matches; | ||
| use rustc_hir::def::DefKind; | ||
| use rustc_hir::def_id::DefId; | ||
| use rustc_middle::ty::layout::{IntegerExt, TyAndLayout}; | ||
| use rustc_middle::ty::{self, AdtDef, Instance, Ty, VariantDef}; | ||
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@@ -17,7 +18,7 @@ use tracing::{info, instrument, trace}; | |
| use super::{ | ||
| CtfeProvenance, FnVal, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy, | ||
| Projectable, Provenance, ReturnAction, ReturnContinuation, Scalar, StackPopInfo, interp_ok, | ||
| throw_ub, throw_ub_custom, | ||
| }; | ||
| use crate::interpret::EnteredTraceSpan; | ||
| use crate::{enter_trace_span, fluent_generated as fluent}; | ||
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@@ -349,13 +350,27 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { | |
| ) -> InterpResult<'tcx> { | ||
| let _trace = enter_trace_span!(M, step::init_stack_frame, %instance, tracing_separate_thread = Empty); | ||
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| // The check for the DefKind is so that we don't request the fn_sig of a closure. | ||
| // Otherwise, we hit: | ||
| // | ||
| // DefId(1:180 ~ std[269c]::rt::lang_start_internal::{closure#0}) does not have a "fn_sig" | ||
| let (fixed_count, callee_c_variadic_args) = | ||
| if matches!(self.tcx.def_kind(instance.def_id()), DefKind::Fn) | ||
| && let callee_fn_sig = self.tcx.fn_sig(instance.def_id()).skip_binder() | ||
| && callee_fn_sig.c_variadic() | ||
|
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There was a problem hiding this comment. This is very odd and seems to break our usual abstractions. How does codegen deal with this?
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Author
There was a problem hiding this comment. I'm not sure, I asked in #t-compiler/help > no `fn_sig`for `lang_start_internal` closure. My impression is that those functions just never get
Contributor
Author
There was a problem hiding this comment. Apparently checking for the |
||
| { | ||
| // A mismatch in caller and callee fixed_count will error below. | ||
| let fixed_count = callee_fn_sig.inputs().skip_binder().len(); | ||
| let extra_tys = caller_fn_abi.args[caller_fn_abi.fixed_count as usize..] | ||
| .iter() | ||
| .map(|arg_abi| arg_abi.layout.ty); | ||
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| (fixed_count, self.tcx.mk_type_list_from_iter(extra_tys)) | ||
| } else { | ||
| (caller_fn_abi.fixed_count.try_into().unwrap(), ty::List::empty()) | ||
| }; | ||
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| let callee_fn_abi = self.fn_abi_of_instance(instance, callee_c_variadic_args)?; | ||
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| if caller_fn_abi.conv != callee_fn_abi.conv { | ||
| throw_ub_custom!( | ||
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@@ -365,6 +380,20 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { | |
| ) | ||
| } | ||
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| if caller_fn_abi.c_variadic != callee_fn_abi.c_variadic { | ||
| throw_ub!(CVariadicMismatch { | ||
| caller_is_c_variadic: caller_fn_abi.c_variadic, | ||
| callee_is_c_variadic: callee_fn_abi.c_variadic, | ||
| }); | ||
| } | ||
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| if caller_fn_abi.c_variadic && caller_fn_abi.fixed_count != callee_fn_abi.fixed_count { | ||
| throw_ub!(CVariadicFixedCountMismatch { | ||
| caller: caller_fn_abi.fixed_count, | ||
| callee: callee_fn_abi.fixed_count, | ||
| }); | ||
| } | ||
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| // Check that all target features required by the callee (i.e., from | ||
| // the attribute `#[target_feature(enable = ...)]`) are enabled at | ||
| // compile time. | ||
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@@ -436,16 +465,54 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> { | |
| // this is a single iterator (that handles `spread_arg`), then | ||
| // `pass_argument` would be the loop body. It takes care to | ||
| // not advance `caller_iter` for ignored arguments. | ||
| let mut callee_args_abis = if caller_fn_abi.c_variadic { | ||
| // Only the fixed arguments are passed normally. C-variadic functions cannot be | ||
| // `extern "Rust"` and `#[track_caller]` can only be applied to `extern "Rust"`, to | ||
| // the extra caller location argument is not relevant here. | ||
| assert!(!instance.def.requires_caller_location(*self.tcx)); | ||
| callee_fn_abi.args[..fixed_count].iter().enumerate() | ||
| } else { | ||
| // NOTE: this handles the extra caller location argument that is passed when | ||
| // `#[track_caller]` is used. The `fixed_count` does not account for this argument. | ||
| // This attribute is only allowed on `extern "Rust"` functions, so the c-variadic | ||
| // case does not need to handle the extra argument. | ||
| callee_fn_abi.args.iter().enumerate() | ||
| }; | ||
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||
| let mut it = body.args_iter().peekable(); | ||
| while let Some(local) = it.next() { | ||
| // Construct the destination place for this argument. At this point all | ||
| // locals are still dead, so we cannot construct a `PlaceTy`. | ||
| let dest = mir::Place::from(local); | ||
| // `layout_of_local` does more than just the instantiation we need to get the | ||
| // type, but the result gets cached so this avoids calling the instantiation | ||
| // query *again* the next time this local is accessed. | ||
| let ty = self.layout_of_local(self.frame(), local, None)?.ty; | ||
| if caller_fn_abi.c_variadic && it.peek().is_none() { | ||
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| // This is the last callee-side argument of a variadic function. | ||
| // This argument is a VaList holding the remaining caller-side arguments. | ||
| self.storage_live(local)?; | ||
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| let place = self.eval_place(dest)?; | ||
| let mplace = self.force_allocation(&place)?; | ||
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| // Consume the remaining arguments by putting them into the variable argument | ||
| // list. | ||
| let varargs = self.allocate_varargs(&mut caller_args)?; | ||
| // When the frame is dropped, these variable arguments are deallocated. | ||
| self.frame_mut().va_list = varargs.clone(); | ||
| let key = self.va_list_ptr(varargs.into()); | ||
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| // Zero the VaList, so it is fully initialized. | ||
| self.write_bytes_ptr( | ||
| mplace.ptr(), | ||
| (0..mplace.layout.size.bytes()).map(|_| 0u8), | ||
| )?; | ||
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| // Store the "key" pointer in the right field. | ||
| let key_mplace = self.va_list_key_field(&mplace)?; | ||
| self.write_pointer(key, &key_mplace)?; | ||
| } else if Some(local) == body.spread_arg { | ||
| // Make the local live once, then fill in the value field by field. | ||
| self.storage_live(local)?; | ||
| // Must be a tuple | ||
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