r318556 - Loosen -Wempty-body warning

[Hans Wennborg via cfe-commits]

We're still seeing some in macro-related code. From Chromium:

../../third_party/ffmpeg/libavcodec/bitstream.c(169,5):  error: if
statement has empty body [-Werror,-Wempty-body]
    ff_dlog(NULL, "new table index=%d size=%d\n", table_index, table_size);
    ^
../../third_party/ffmpeg\libavutil/internal.h(276,80):  note: expanded
from macro 'ff_dlog'
#   define ff_dlog(ctx, ...) do { if (0) av_log(ctx, AV_LOG_DEBUG,
__VA_ARGS__); } while (0)
                                                                               ^
../../third_party/ffmpeg/libavcodec/bitstream.c(169,5):  note: put the
semicolon on a separate line to silence this warning

(See https://build.chromium.org/p/chromium.clang/builders/ToTWin/builds/420)

On Fri, Nov 17, 2017 at 1:33 PM, Reid Kleckner via cfe-commits
<cfe-commits at lists.llvm.org> wrote:
> Author: rnk
> Date: Fri Nov 17 13:33:28 2017
> New Revision: 318556
>
> URL: http://llvm.org/viewvc/llvm-project?rev=318556&view=rev
> Log:
> Loosen -Wempty-body warning
>
> Do not show it when `if` or `else` come from macros.
> E.g.,
>
>     #define USED(A) if (A); else
>     #define SOME_IF(A) if (A)
>
>     void test() {
>       // No warnings are shown in those cases now.
>       USED(0);
>       SOME_IF(0);
>     }
>
> Patch by Ilya Biryukov!
>
> Differential Revision: https://reviews.llvm.org/D40185
>
> Modified:
>     cfe/trunk/include/clang/Sema/Sema.h
>     cfe/trunk/lib/Parse/ParseStmt.cpp
>     cfe/trunk/lib/Sema/SemaChecking.cpp
>     cfe/trunk/lib/Sema/SemaStmt.cpp
>     cfe/trunk/test/SemaCXX/warn-empty-body.cpp
>
> Modified: cfe/trunk/include/clang/Sema/Sema.h
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=318556&r1=318555&r2=318556&view=diff
> ==============================================================================
> --- cfe/trunk/include/clang/Sema/Sema.h (original)
> +++ cfe/trunk/include/clang/Sema/Sema.h Fri Nov 17 13:33:28 2017
> @@ -9690,6 +9690,7 @@ public:
>    class ConditionResult {
>      Decl *ConditionVar;
>      FullExprArg Condition;
> +    SourceLocation RParenLoc;
>      bool Invalid;
>      bool HasKnownValue;
>      bool KnownValue;
> @@ -9713,6 +9714,9 @@ public:
>        return std::make_pair(cast_or_null<VarDecl>(ConditionVar),
>                              Condition.get());
>      }
> +
> +    void setRParenLoc(SourceLocation Loc) { RParenLoc = Loc; }
> +
>      llvm::Optional<bool> getKnownValue() const {
>        if (!HasKnownValue)
>          return None;
>
> Modified: cfe/trunk/lib/Parse/ParseStmt.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Parse/ParseStmt.cpp?rev=318556&r1=318555&r2=318556&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Parse/ParseStmt.cpp (original)
> +++ cfe/trunk/lib/Parse/ParseStmt.cpp Fri Nov 17 13:33:28 2017
> @@ -1101,6 +1101,7 @@ bool Parser::ParseParenExprOrCondition(S
>
>    // Otherwise the condition is valid or the rparen is present.
>    T.consumeClose();
> +  Cond.setRParenLoc(T.getCloseLocation());
>
>    // Check for extraneous ')'s to catch things like "if (foo())) {".  We know
>    // that all callers are looking for a statement after the condition, so ")"
>
> Modified: cfe/trunk/lib/Sema/SemaChecking.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaChecking.cpp?rev=318556&r1=318555&r2=318556&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaChecking.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaChecking.cpp Fri Nov 17 13:33:28 2017
> @@ -11821,7 +11821,7 @@ static bool ShouldDiagnoseEmptyStmtBody(
>
>    // Get line numbers of statement and body.
>    bool StmtLineInvalid;
> -  unsigned StmtLine = SourceMgr.getPresumedLineNumber(StmtLoc,
> +  unsigned StmtLine = SourceMgr.getSpellingLineNumber(StmtLoc,
>                                                        &StmtLineInvalid);
>    if (StmtLineInvalid)
>      return false;
>
> Modified: cfe/trunk/lib/Sema/SemaStmt.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaStmt.cpp?rev=318556&r1=318555&r2=318556&view=diff
> ==============================================================================
> --- cfe/trunk/lib/Sema/SemaStmt.cpp (original)
> +++ cfe/trunk/lib/Sema/SemaStmt.cpp Fri Nov 17 13:33:28 2017
> @@ -530,8 +530,7 @@ Sema::ActOnIfStmt(SourceLocation IfLoc,
>    if (elseStmt)
>      DiagnoseEmptyStmtBody(ElseLoc, elseStmt, diag::warn_empty_else_body);
>    else
> -    DiagnoseEmptyStmtBody(CondExpr->getLocEnd(), thenStmt,
> -                          diag::warn_empty_if_body);
> +    DiagnoseEmptyStmtBody(Cond.RParenLoc, thenStmt, diag::warn_empty_if_body);
>
>    return BuildIfStmt(IfLoc, IsConstexpr, InitStmt, Cond, thenStmt, ElseLoc,
>                       elseStmt);
>
> Modified: cfe/trunk/test/SemaCXX/warn-empty-body.cpp
> URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-empty-body.cpp?rev=318556&r1=318555&r2=318556&view=diff
> ==============================================================================
> --- cfe/trunk/test/SemaCXX/warn-empty-body.cpp (original)
> +++ cfe/trunk/test/SemaCXX/warn-empty-body.cpp Fri Nov 17 13:33:28 2017
> @@ -301,3 +301,14 @@ void test7(int x, int y) {
>    if (x) IDENTITY(); // no-warning
>  }
>
> +#define SOME_IF(A) if (A)
> +#define IF_ELSE(A) if (A); else
> +
> +
> +void test_macros() {
> +  SOME_IF(0);
> +  IF_ELSE(0);
> +
> +  IDENTITY(if (0);) // expected-warning{{if statement has empty body}} expected-note{{separate line}}
> +  IDENTITY(if (0); else;) // expected-warning{{else clause has empty body}} expected-note{{separate line}}}
> +}
>
>
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