[StaticAnalyzer] Fix tryExpandAsInteger's failures on PCH macros (#142722)

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

---------

Co-authored-by: Balazs Benics <[email protected]>

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;
+  SmallVector<char> Buffer(T.getLength());
+  // `Preprocessor::getSpelling` can get the spelling of the token regardless of
+  // whether the macro is defined in a PCH or not:
+  StringRef ValueStr = PP.getSpelling(T, Buffer, &InvalidSpelling);
+
+  if (InvalidSpelling)
+    return std::nullopt;
+
   llvm::APInt IntValue;
   constexpr unsigned AutoSenseRadix = 0;
   if (ValueStr.getAsInteger(AutoSenseRadix, IntValue))

clang/test/Analysis/pch_crash.cpp

@@ -0,0 +1,50 @@
+// RUN: rm -rf %t
+// RUN: mkdir -p %t
+// RUN: split-file %s %t
+
+// DEFINE: %{emit-pch-action} = \
+// DEFINE:   %clang_cc1 -x c++ -emit-pch -o %t/header.pch %t/header.h
+
+// DEFINE: %{analyze-action} = \
+// DEFINE:   %clang_analyze_cc1 -include-pch %t/header.pch \
+// DEFINE:   -analyzer-checker=core,apiModeling,unix.StdCLibraryFunctions \
+// DEFINE:   -verify %t/main.cpp
+
+// RUN: %{emit-pch-action} -triple x86_64-apple-macosx10.15.0
+// RUN: %{analyze-action}  -triple x86_64-apple-macosx10.15.0
+// RUN: %{emit-pch-action}
+// RUN: %{analyze-action}
+
+
+//--- header.h
+
+
+// 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
+
+
+//--- main.cpp
+
+
+// Source file
+// expected-no-diagnostics
+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)) {}
+}
+