Add the diagnose_if attribute to clang.
`diagnose_if` can be used to have clang emit either warnings or errors
for function calls that meet user-specified conditions. For example:
```
constexpr int foo(int a)
__attribute__((diagnose_if(a > 10, "configurations with a > 10 are "
"expensive.", "warning")));
int f1 = foo(9);
int f2 = foo(10); // warning: configuration with a > 10 are expensive.
int f3 = foo(f2);
```
It currently only emits diagnostics in cases where the condition is
guaranteed to always be true. So, the following code will emit no
warnings:
```
constexpr int bar(int a) {
foo(a);
return 0;
}
constexpr int i = bar(10);
```
We hope to support optionally emitting diagnostics for cases like that
(and emitting runtime checks) in the future.
Release notes will appear shortly. :)
Differential Revision: https://reviews.llvm.org/D27424
llvm-svn: 291418
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index ffe3566..d2a5e5c 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -168,40 +168,59 @@
Aligned->getSpellingListIndex());
}
-static void instantiateDependentEnableIfAttr(
+static Expr *instantiateDependentFunctionAttrCondition(
Sema &S, const MultiLevelTemplateArgumentList &TemplateArgs,
- const EnableIfAttr *A, const Decl *Tmpl, Decl *New) {
+ const Attr *A, Expr *OldCond, const Decl *Tmpl, FunctionDecl *New) {
Expr *Cond = nullptr;
{
- Sema::ContextRAII SwitchContext(S, cast<FunctionDecl>(New));
+ Sema::ContextRAII SwitchContext(S, New);
EnterExpressionEvaluationContext Unevaluated(S, Sema::ConstantEvaluated);
- ExprResult Result = S.SubstExpr(A->getCond(), TemplateArgs);
+ ExprResult Result = S.SubstExpr(OldCond, TemplateArgs);
if (Result.isInvalid())
- return;
+ return nullptr;
Cond = Result.getAs<Expr>();
}
if (!Cond->isTypeDependent()) {
ExprResult Converted = S.PerformContextuallyConvertToBool(Cond);
if (Converted.isInvalid())
- return;
+ return nullptr;
Cond = Converted.get();
}
SmallVector<PartialDiagnosticAt, 8> Diags;
- if (A->getCond()->isValueDependent() && !Cond->isValueDependent() &&
- !Expr::isPotentialConstantExprUnevaluated(Cond, cast<FunctionDecl>(New),
- Diags)) {
- S.Diag(A->getLocation(), diag::err_enable_if_never_constant_expr);
- for (int I = 0, N = Diags.size(); I != N; ++I)
- S.Diag(Diags[I].first, Diags[I].second);
- return;
+ if (OldCond->isValueDependent() && !Cond->isValueDependent() &&
+ !Expr::isPotentialConstantExprUnevaluated(Cond, New, Diags)) {
+ S.Diag(A->getLocation(), diag::err_attr_cond_never_constant_expr) << A;
+ for (const auto &P : Diags)
+ S.Diag(P.first, P.second);
+ return nullptr;
}
+ return Cond;
+}
- EnableIfAttr *EIA = new (S.getASTContext())
- EnableIfAttr(A->getLocation(), S.getASTContext(), Cond,
- A->getMessage(),
- A->getSpellingListIndex());
- New->addAttr(EIA);
+static void instantiateDependentEnableIfAttr(
+ Sema &S, const MultiLevelTemplateArgumentList &TemplateArgs,
+ const EnableIfAttr *EIA, const Decl *Tmpl, FunctionDecl *New) {
+ Expr *Cond = instantiateDependentFunctionAttrCondition(
+ S, TemplateArgs, EIA, EIA->getCond(), Tmpl, New);
+
+ if (Cond)
+ New->addAttr(new (S.getASTContext()) EnableIfAttr(
+ EIA->getLocation(), S.getASTContext(), Cond, EIA->getMessage(),
+ EIA->getSpellingListIndex()));
+}
+
+static void instantiateDependentDiagnoseIfAttr(
+ Sema &S, const MultiLevelTemplateArgumentList &TemplateArgs,
+ const DiagnoseIfAttr *DIA, const Decl *Tmpl, FunctionDecl *New) {
+ Expr *Cond = instantiateDependentFunctionAttrCondition(
+ S, TemplateArgs, DIA, DIA->getCond(), Tmpl, New);
+
+ if (Cond)
+ New->addAttr(new (S.getASTContext()) DiagnoseIfAttr(
+ DIA->getLocation(), S.getASTContext(), Cond, DIA->getMessage(),
+ DIA->getDiagnosticType(), DIA->getArgDependent(), New,
+ DIA->getSpellingListIndex()));
}
// Constructs and adds to New a new instance of CUDALaunchBoundsAttr using
@@ -335,7 +354,13 @@
if (const auto *EnableIf = dyn_cast<EnableIfAttr>(TmplAttr)) {
instantiateDependentEnableIfAttr(*this, TemplateArgs, EnableIf, Tmpl,
- New);
+ cast<FunctionDecl>(New));
+ continue;
+ }
+
+ if (const auto *DiagnoseIf = dyn_cast<DiagnoseIfAttr>(TmplAttr)) {
+ instantiateDependentDiagnoseIfAttr(*this, TemplateArgs, DiagnoseIf, Tmpl,
+ cast<FunctionDecl>(New));
continue;
}