Generalize -Wempty-body: warn when statement body is empty (closes: PR11329)
* if, switch, range-based for: warn if semicolon is on the same line.
* for, while: warn if semicolon is on the same line and either next
statement is compound statement or next statement has more
indentation.
Replacing the semicolon with {} or moving the semicolon to the next
line will always silence the warning.
Tests from SemaCXX/if-empty-body.cpp merged into SemaCXX/warn-empty-body.cpp.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@150515 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/SemaChecking.cpp b/lib/Sema/SemaChecking.cpp
index cf04695..3393cf7 100644
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@@ -4827,3 +4827,130 @@
}
}
}
+
+//===--- CHECK: Empty statement body (-Wempty-body) ---------------------===//
+
+namespace {
+bool ShouldDiagnoseEmptyStmtBody(const SourceManager &SourceMgr,
+ SourceLocation StmtLoc,
+ const NullStmt *Body) {
+ // Do not warn if the body is a macro that expands to nothing, e.g:
+ //
+ // #define CALL(x)
+ // if (condition)
+ // CALL(0);
+ //
+ if (Body->hasLeadingEmptyMacro())
+ return false;
+
+ // Get line numbers of statement and body.
+ bool StmtLineInvalid;
+ unsigned StmtLine = SourceMgr.getSpellingLineNumber(StmtLoc,
+ &StmtLineInvalid);
+ if (StmtLineInvalid)
+ return false;
+
+ bool BodyLineInvalid;
+ unsigned BodyLine = SourceMgr.getSpellingLineNumber(Body->getSemiLoc(),
+ &BodyLineInvalid);
+ if (BodyLineInvalid)
+ return false;
+
+ // Warn if null statement and body are on the same line.
+ if (StmtLine != BodyLine)
+ return false;
+
+ return true;
+}
+} // Unnamed namespace
+
+void Sema::DiagnoseEmptyStmtBody(SourceLocation StmtLoc,
+ const Stmt *Body,
+ unsigned DiagID) {
+ // Since this is a syntactic check, don't emit diagnostic for template
+ // instantiations, this just adds noise.
+ if (CurrentInstantiationScope)
+ return;
+
+ // The body should be a null statement.
+ const NullStmt *NBody = dyn_cast<NullStmt>(Body);
+ if (!NBody)
+ return;
+
+ // Do the usual checks.
+ if (!ShouldDiagnoseEmptyStmtBody(SourceMgr, StmtLoc, NBody))
+ return;
+
+ Diag(NBody->getSemiLoc(), DiagID);
+ Diag(NBody->getSemiLoc(), diag::note_empty_body_on_separate_line);
+}
+
+void Sema::DiagnoseEmptyLoopBody(const Stmt *S,
+ const Stmt *PossibleBody) {
+ assert(!CurrentInstantiationScope); // Ensured by caller
+
+ SourceLocation StmtLoc;
+ const Stmt *Body;
+ unsigned DiagID;
+ if (const ForStmt *FS = dyn_cast<ForStmt>(S)) {
+ StmtLoc = FS->getRParenLoc();
+ Body = FS->getBody();
+ DiagID = diag::warn_empty_for_body;
+ } else if (const WhileStmt *WS = dyn_cast<WhileStmt>(S)) {
+ StmtLoc = WS->getCond()->getSourceRange().getEnd();
+ Body = WS->getBody();
+ DiagID = diag::warn_empty_while_body;
+ } else
+ return; // Neither `for' nor `while'.
+
+ // The body should be a null statement.
+ const NullStmt *NBody = dyn_cast<NullStmt>(Body);
+ if (!NBody)
+ return;
+
+ // Skip expensive checks if diagnostic is disabled.
+ if (Diags.getDiagnosticLevel(DiagID, NBody->getSemiLoc()) ==
+ DiagnosticsEngine::Ignored)
+ return;
+
+ // Do the usual checks.
+ if (!ShouldDiagnoseEmptyStmtBody(SourceMgr, StmtLoc, NBody))
+ return;
+
+ // `for(...);' and `while(...);' are popular idioms, so in order to keep
+ // noise level low, emit diagnostics only if for/while is followed by a
+ // CompoundStmt, e.g.:
+ // for (int i = 0; i < n; i++);
+ // {
+ // a(i);
+ // }
+ // or if for/while is followed by a statement with more indentation
+ // than for/while itself:
+ // for (int i = 0; i < n; i++);
+ // a(i);
+ bool ProbableTypo = isa<CompoundStmt>(PossibleBody);
+ if (!ProbableTypo) {
+ bool BodyColInvalid;
+ unsigned BodyCol = SourceMgr.getPresumedColumnNumber(
+ PossibleBody->getLocStart(),
+ &BodyColInvalid);
+ if (BodyColInvalid)
+ return;
+
+ bool StmtColInvalid;
+ unsigned StmtCol = SourceMgr.getPresumedColumnNumber(
+ S->getLocStart(),
+ &StmtColInvalid);
+ if (StmtColInvalid)
+ return;
+
+ if (BodyCol > StmtCol)
+ ProbableTypo = true;
+ }
+
+ if (ProbableTypo) {
+ Diag(NBody->getSemiLoc(), DiagID);
+ Diag(NBody->getSemiLoc(), diag::note_empty_body_on_separate_line);
+ }
+}
+