[StaticAnalyzer] Fix tryExpandAsInteger's failures on macros from PCHs

The function `tryExpandAsInteger` attempts to extract an integer from
a macro definition.  Previously, the attempt would fail when the macro
is from a PCH, because the function tried to access the text buffer of
the source file, which does not exist in case of PCHs.  The fix uses
`Preprocessor::getSpelling`, which works in either cases.

rdar://151403070

Author: ziqingluo-90

clang/lib/StaticAnalyzer/Core/CheckerHelpers.cpp

@@ -129,11 +129,19 @@ std::optional<int> tryExpandAsInteger(StringRef Macro, const Preprocessor &PP) {
 
   // Parse an integer at the end of the macro definition.
   const Token &T = FilteredTokens.back();
-  // FIXME: EOF macro token coming from a PCH file on macOS while marked as
-  //        literal, doesn't contain any literal data
-  if (!T.isLiteral() || !T.getLiteralData())
+
+  if (!T.isLiteral())
     return std::nullopt;
-  StringRef ValueStr = StringRef(T.getLiteralData(), T.getLength());
+
+  bool InvalidSpelling = false;
+  // `Preprocessor::getSpelling` can get the spelling of the token regardless of
+  // whether the macro is defined in a PCH or not:
+  std::string Spelling = PP.getSpelling(T, &InvalidSpelling);
+
+  if (InvalidSpelling)
+    return std::nullopt;
+
+  StringRef ValueStr(Spelling);
   llvm::APInt IntValue;
   constexpr unsigned AutoSenseRadix = 0;
   if (ValueStr.getAsInteger(AutoSenseRadix, IntValue))

clang/test/Analysis/pch_crash.cpp

@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -triple x86_64-apple-macosx10.15.0 -emit-pch -o %t %s
+// RUN: %clang_analyze_cc1 -triple x86_64-apple-macosx10.15.0 -include-pch %t \
+// RUN:   -analyzer-checker=core,apiModeling,unix.StdCLibraryFunctions -verify %s
+//
+// RUN: %clang_cc1 -emit-pch -o %t %s
+// RUN: %clang_analyze_cc1 -include-pch %t \
+// RUN:   -analyzer-checker=core,apiModeling,unix.StdCLibraryFunctions -verify %s
+
+// expected-no-diagnostics
+
+#ifndef HEADER
+#define HEADER
+// Pre-compiled header
+
+int foo();
+
+// Literal data for macro values will be null as they are defined in a PCH
+#define EOF -1
+#define AT_FDCWD -2
+
+#else
+// Source file
+
+int test() {
+  // we need a function call here to initiate erroneous routine
+  return foo(); // no-crash
+}
+
+// Test that StdLibraryFunctionsChecker can obtain the definition of
+// AT_FDCWD even if it is from a PCH:
+int faccessat(int, const char *, int, int);
+
+void test_faccessat() {
+  char fileSystemPath[10] = { 0 };
+
+  if (0 != faccessat(AT_FDCWD, fileSystemPath, 2, 0x0030)) {}
+}
+
+#endif