[clang] Fix assertion with invalid embed limit parameter value (#157896)

If a negative value was given we would fail to skip till the end of the
directive and trip a failed assertion.

Fixes #157842

Author: Fznamznon

clang/docs/ReleaseNotes.rst

@@ -308,6 +308,8 @@ Bug Fixes in This Version
 - Builtin elementwise operators now accept vector arguments that have different
   qualifiers on their elements. For example, vector of 4 ``const float`` values
   and vector of 4 ``float`` values. (#GH155405)
+- Fixed a failed assertion with a negative limit parameter value inside of
+  ``__has_embed``. (#GH157842)
 
 Bug Fixes to Compiler Builtins
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

clang/lib/Lex/PPDirectives.cpp

@@ -3746,6 +3746,8 @@ Preprocessor::LexEmbedParameters(Token &CurTok, bool ForHasEmbed) {
       if (Result.isNegative()) {
         Diag(CurTok, diag::err_requires_positive_value)
             << toString(Result, 10) << /*positive*/ 0;
+        if (CurTok.isNot(tok::eod))
+          DiscardUntilEndOfDirective(CurTok);
         return std::nullopt;
       }
       return Result.getLimitedValue();

clang/test/Preprocessor/embed___has_embed_parsing_errors.c

@@ -238,3 +238,12 @@
 #if __has_embed("media/art.txt" if_empty))
 #endif
 
+// expected-error@+2 {{invalid value '-1'; must be positive}} \
+   expected-error@+2 {{expected value in expression}}
+#if __has_embed (__FILE__ limit(-1))
+#endif
+
+// expected-error@+2 {{invalid value '-100000000000000000'; must be positive}}\
+   expected-error@+2 {{expected value in expression}}
+#if __has_embed (__FILE__ limit(-100000000000000000)) != __STDC_EMBED_NOT_FOUND__
+#endif