Fix for #pragma warning to work correctly with "1-4:" specifiers

[andreybokhanko]

Summary

Bug fix for PR23577 (https://llvm.org/bugs/show_bug.cgi?id=23577#c0).

"1-4" specifiers are returned as numeric constants, not identifiers, and should be treated as such. Currently pragma handler incorrectly assumes that they are returned as identifiers.

[rnk]

Can you add a -E test that verifies that these pragmas roundtrip through the pre-processor?

lib/Lex/Pragma.cpp

1075

Make sure the SmallString has the same lifetime as Specifier.

1091

utostr returns a std::string, so this would be a use-after-free. Use getSpelling() to get a StringRef that points into the original source code so we don't need memory allocation. You'll need to supply a SmallString, but 99% of the time it'll be unused.

[andreybokhanko]

Reid, thank you for the review!

I fixed the use-after-free bug you found (good catch, BTW!) I also created a test that checks -E (not sure this is exactly what you wanted; let me know if I misunderstood you).

[rnk]

test/Preprocessor/pragma_microsoft_E.c

1–3 ↗

(On Diff #26147)

Rather than copy-pasting the file, you can actually have multiple RUN lines in a single test. So back in pragma_microsoft.c you can add the same RUN line you have here and the CHECK lines and it'll all work.

83 ↗

(On Diff #26147)

You should check that the warning pragmas roundtrip through the preprocessor, though.

[andreybokhanko]

Test updated according to Reid's comments.

[andreybokhanko]

test/Preprocessor/pragma_microsoft_E.c

83 ↗

(On Diff #26147)

Reid, sorry for a noob question -- what do you mean by checking "roundtrip through the preprocessor"? Is there an existing test I can use as an example?

In the updated patch I added CHECKs for preprocessor's output -- is this what you meant?

[rnk]

Yes, check lines for pragma warning 1.

Sent from phone

[andreybokhanko]

Updated patch has these checks:

CHECK: #pragma warning(pop)
#pragma warning(1: 123)
CHECK: #pragma warning(1: 123)
#pragma warning(2: 234 567)
CHECK: #pragma warning(2: 234 567)
#pragma warning(3: 123; 4: 678)
CHECK: #pragma warning(3: 123)
CHECK: #pragma warning(4: 678)
#pragma warning(5: 123) expected-warning {{expected 'push', 'pop', 'default', 'disable', 'error', 'once', 'suppress', 1, 2, 3, or 4}}

[rnk]

lgtm, thanks!

[andreybokhanko]

Reid, thank you for the quick and thoughtful review! This is my first ever clang fix and it is very nice to get such a good reception.

I don't have commit rights yet; Alexander [Musman], could you, please, commit the fix?

lib/Lex/Pragma.cpp

 #include "clang/Basic/SourceManager.h"
 #include "clang/Lex/HeaderSearch.h"
 #include "clang/Lex/LexDiagnostic.h"
 #include "clang/Lex/LiteralSupport.h"
 #include "clang/Lex/MacroInfo.h"
 #include "clang/Lex/Preprocessor.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringSwitch.h"
+#include "llvm/ADT/StringExtras.h"
 #include "llvm/Support/CrashRecoveryContext.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <algorithm>
 using namespace clang;
 
 #include "llvm/Support/raw_ostream.h"
 
 // Out-of-line destructor to provide a home for the class.
void HandlePragma(Preprocessor &PP, PragmaIntroducerKind Introducer,
     PP.Lex(Tok);
     if (Tok.isNot(tok::l_paren)) {
       PP.Diag(Tok, diag::warn_pragma_warning_expected) << "(";
       return;
     }
 
     PP.Lex(Tok);
     IdentifierInfo *II = Tok.getIdentifierInfo();
-    if (!II) {
-      PP.Diag(Tok, diag::warn_pragma_warning_spec_invalid);
-      return;
-    }
 
-    if (II->isStr("push")) {
+    if (II && II->isStr("push")) {
       // #pragma warning( push[ ,n ] )
       int Level = -1;
       PP.Lex(Tok);
       if (Tok.is(tok::comma)) {
         PP.Lex(Tok);
         uint64_t Value;
         if (Tok.is(tok::numeric_constant) &&
             PP.parseSimpleIntegerLiteral(Tok, Value))
           Level = int(Value);
         if (Level < 0 || Level > 4) {
           PP.Diag(Tok, diag::warn_pragma_warning_push_level);
           return;
         }
       }
       if (Callbacks)
         Callbacks->PragmaWarningPush(DiagLoc, Level);
-    } else if (II->isStr("pop")) {
+    } else if (II && II->isStr("pop")) {
       // #pragma warning( pop )
       PP.Lex(Tok);
       if (Callbacks)
         Callbacks->PragmaWarningPop(DiagLoc);
     } else {
       // #pragma warning( warning-specifier : warning-number-list
       //                  [; warning-specifier : warning-number-list...] )
       while (true) {
         II = Tok.getIdentifierInfo();
-        if (!II) {
+        if (!II && !Tok.is(tok::numeric_constant)) {
           PP.Diag(Tok, diag::warn_pragma_warning_spec_invalid);
           return;
         }
 
         // Figure out which warning specifier this is.
-        StringRef Specifier = II->getName();
-        bool SpecifierValid =
-            llvm::StringSwitch<bool>(Specifier)
-                .Cases("1", "2", "3", "4", true)
-                .Cases("default", "disable", "error", "once", "suppress", true)
+        bool SpecifierValid;
+        StringRef Specifier;
+        if (II) {
+          Specifier = II->getName();
+          SpecifierValid = llvm::StringSwitch<bool>(Specifier)
+                               .Cases("default", "disable", "error", "once",
+                                      "suppress", true)
                                .Default(false);
+          // If we read a correct specifier, snatch next token (that should be
+          // ":", checked later).
+          if (SpecifierValid)
+            PP.Lex(Tok);
+        } else {
+          // Token is a numeric constant. It should be either 1, 2, 3 or 4.
+          uint64_t Value;
+          if (PP.parseSimpleIntegerLiteral(Tok, Value)) {
+            SpecifierValid = (Value >= 1) && (Value <= 4);
+            Specifier = llvm::utostr(Value);
+          } else
+            SpecifierValid = false;
+          // Next token already snatched by parseSimpleIntegerLiteral.
+        }
+
         if (!SpecifierValid) {
           PP.Diag(Tok, diag::warn_pragma_warning_spec_invalid);
           return;
         }
-        PP.Lex(Tok);
         if (Tok.isNot(tok::colon)) {
           PP.Diag(Tok, diag::warn_pragma_warning_expected) << ":";
           return;
         }
 
         // Collect the warning ids.
         SmallVector<int, 4> Ids;
         PP.Lex(Tok);

test/Preprocessor/pragma_microsoft.c

 #pragma detect_mismatch("test", "1")
 #pragma detect_mismatch()  // expected-error {{expected string literal in pragma detect_mismatch}}
 #pragma detect_mismatch("test") // expected-error {{pragma detect_mismatch is malformed; it requires two comma-separated string literals}}
 #pragma detect_mismatch("test", 1) // expected-error {{expected string literal in pragma detect_mismatch}}
 #pragma detect_mismatch("test", BAR)
 
 // __pragma
 
-__pragma(comment(linker," bar=" BAR))                                            
+__pragma(comment(linker," bar=" BAR))
 
 #define MACRO_WITH__PRAGMA { \
   __pragma(warning(push)); \
   __pragma(warning(disable: 10000)); \
   1 + (2 > 3) ? 4 : 5; \
   __pragma(warning(pop)); \
 }
 

 #pragma warning(push)
 #pragma warning(push, 1)
 #pragma warning(disable : 4705)
 #pragma warning(disable : 123 456 789 ; error : 321)
 #pragma warning(once : 321)
 #pragma warning(suppress : 321)
 #pragma warning(default : 321)
 #pragma warning(pop)
+#pragma warning(1: 123)
+#pragma warning(2: 234 567)
+#pragma warning(3: 123; 4: 678)
+#pragma warning(5: 123) // expected-warning {{expected 'push', 'pop', 'default', 'disable', 'error', 'once', 'suppress', 1, 2, 3, or 4}}
 
 #pragma warning(push, 0)
 // FIXME: We could probably support pushing warning level 0.
 #pragma warning(pop)
 
 #pragma warning  // expected-warning {{expected '('}}
 #pragma warning(   // expected-warning {{expected 'push', 'pop', 'default', 'disable', 'error', 'once', 'suppress', 1, 2, 3, or 4}}
 #pragma warning()   // expected-warning {{expected 'push', 'pop', 'default', 'disable', 'error', 'once', 'suppress', 1, 2, 3, or 4}}