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[clang][#51931] Enable -Wdeclaration-after-statement for all C versions

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-Wdeclaration-after-statement currently only outputs an diagnostic if the user is compiling in C versions older than C99, even if the warning was explicitly requested by the user.
This patch makes the warning also available in later C versions. If the C version is C99 or later it is simply a normal warning that is disabled by default (as it is valid C99) and has to be enabled by users. In older versions it remains an extension warning, and therefore affected by -pedantic.

The above behaviour also matches GCCs behaviour.

Fixes https://bugs.llvm.org/show_bug.cgi?id=51931

Differential Revision: https://reviews.llvm.org/D114787
This commit is contained in:
Markus Böck
2022-01-06 11:26:03 +01:00
parent 1773dddadf
commit 118f966b46
4 changed files with 40 additions and 6 deletions
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1
clang/include/clang/Basic/DiagnosticGroups.td
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@@ -241,6 +241,7 @@ def Documentation : DiagGroup<"documentation",
def EmptyBody : DiagGroup<"empty-body">;
def Exceptions : DiagGroup<"exceptions">;
def DeclarationAfterStatement : DiagGroup<"declaration-after-statement">;
def GNUEmptyInitializer : DiagGroup<"gnu-empty-initializer">;
def GNUEmptyStruct : DiagGroup<"gnu-empty-struct">;

7
clang/include/clang/Basic/DiagnosticSemaKinds.td
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@@ -9861,8 +9861,11 @@ def err_constant_integer_arg_type : Error<
"argument to %0 must be a constant integer">;
def ext_mixed_decls_code : Extension<
"ISO C90 forbids mixing declarations and code">,
InGroup<DiagGroup<"declaration-after-statement">>;
"mixing declarations and code is a C99 extension">,
InGroup<DeclarationAfterStatement>;
def warn_mixed_decls_code : Warning<
"mixing declarations and code is incompatible with standards before C99">,
InGroup<DeclarationAfterStatement>, DefaultIgnore;
def err_non_local_variable_decl_in_for : Error<
"declaration of non-local variable in 'for' loop">;

10
clang/lib/Sema/SemaStmt.cpp
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@@ -410,9 +410,10 @@ StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
ArrayRef<Stmt *> Elts, bool isStmtExpr) {
const unsigned NumElts = Elts.size();
// If we're in C89 mode, check that we don't have any decls after stmts. If
// so, emit an extension diagnostic.
if (!getLangOpts().C99 && !getLangOpts().CPlusPlus) {
// If we're in C mode, check that we don't have any decls after stmts. If
// so, emit an extension diagnostic in C89 and potentially a warning in later
// versions.
if (!getLangOpts().CPlusPlus) {
// Note that __extension__ can be around a decl.
unsigned i = 0;
// Skip over all declarations.
@@ -425,7 +426,8 @@ StmtResult Sema::ActOnCompoundStmt(SourceLocation L, SourceLocation R,
if (i != NumElts) {
Decl *D = *cast<DeclStmt>(Elts[i])->decl_begin();
Diag(D->getLocation(), diag::ext_mixed_decls_code);
Diag(D->getLocation(), !getLangOpts().C99 ? diag::ext_mixed_decls_code
: diag::warn_mixed_decls_code);
}
}

28
clang/test/Sema/warn-mixed-decls.c Normal file
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@@ -0,0 +1,28 @@
/* RUN: %clang_cc1 -fsyntax-only -verify -std=c89 -pedantic %s
*/
/* RUN: %clang_cc1 -fsyntax-only -verify -std=c99 -Wdeclaration-after-statement %s
*/
/* Should not emit diagnostic when not pedantic, not enabled or in C++ Code*/
/* RUN: %clang_cc1 -fsyntax-only -verify=none -std=c89 %s
*/
/* RUN: %clang_cc1 -fsyntax-only -verify=none -std=c99 %s
*/
/* RUN: %clang_cc1 -fsyntax-only -verify=none -x c++ %s
*/
/* RUN: %clang_cc1 -fsyntax-only -verify=none -x c++ -Wdeclaration-after-statement %s
*/
/* none-no-diagnostics */
int foo(int i)
{
i += 1;
int f = i;
#if __STDC_VERSION__ < 199901L
/* expected-warning@-2 {{mixing declarations and code is a C99 extension}}*/
#else
/* expected-warning@-4 {{mixing declarations and code is incompatible with standards before C99}}*/
#endif
return f;
}