Reapply Logging: make os_log buffer size an integer constant expression.

The size of an os_log buffer is known at any stage of compilation, so making it
a constant expression means that the common idiom of declaring a buffer for it
won't result in a VLA. That allows the compiler to skip saving and restoring
the stack pointer around such buffers.

This also moves the OSLog and other FormatString helpers from
libclangAnalysis to libclangAST to avoid a circular dependency.

llvm-svn: 345971

1 files changed, 79 insertions, 0 deletions

diff --git a/clang/lib/AST/FormatStringParsing.h b/clang/lib/AST/FormatStringParsing.h
new file mode 100644
index 00000000000..91fab155e4c
--- /dev/null
+++ b/clang/lib/AST/FormatStringParsing.h
@@ -0,0 +1,79 @@
+#ifndef LLVM_CLANG_LIB_ANALYSIS_FORMATSTRINGPARSING_H
+#define LLVM_CLANG_LIB_ANALYSIS_FORMATSTRINGPARSING_H
+
+#include "clang/AST/ASTContext.h"
+#include "clang/AST/Type.h"
+#include "clang/AST/FormatString.h"
+
+namespace clang {
+
+class LangOptions;
+
+template <typename T>
+class UpdateOnReturn {
+  T &ValueToUpdate;
+  const T &ValueToCopy;
+public:
+  UpdateOnReturn(T &valueToUpdate, const T &valueToCopy)
+    : ValueToUpdate(valueToUpdate), ValueToCopy(valueToCopy) {}
+
+  ~UpdateOnReturn() {
+    ValueToUpdate = ValueToCopy;
+  }
+};
+
+namespace analyze_format_string {
+
+OptionalAmount ParseAmount(const char *&Beg, const char *E);
+OptionalAmount ParseNonPositionAmount(const char *&Beg, const char *E,
+                                      unsigned &argIndex);
+
+OptionalAmount ParsePositionAmount(FormatStringHandler &H,
+                                   const char *Start, const char *&Beg,
+                                   const char *E, PositionContext p);
+
+bool ParseFieldWidth(FormatStringHandler &H,
+                     FormatSpecifier &CS,
+                     const char *Start, const char *&Beg, const char *E,
+                     unsigned *argIndex);
+
+bool ParseArgPosition(FormatStringHandler &H,
+                      FormatSpecifier &CS, const char *Start,
+                      const char *&Beg, const char *E);
+
+/// Returns true if a LengthModifier was parsed and installed in the
+/// FormatSpecifier& argument, and false otherwise.
+bool ParseLengthModifier(FormatSpecifier &FS, const char *&Beg, const char *E,
+                         const LangOptions &LO, bool IsScanf = false);
+
+/// Returns true if the invalid specifier in \p SpecifierBegin is a UTF-8
+/// string; check that it won't go further than \p FmtStrEnd and write
+/// up the total size in \p Len.
+bool ParseUTF8InvalidSpecifier(const char *SpecifierBegin,
+                               const char *FmtStrEnd, unsigned &Len);
+
+template <typename T> class SpecifierResult {
+  T FS;
+  const char *Start;
+  bool Stop;
+public:
+  SpecifierResult(bool stop = false)
+  : Start(nullptr), Stop(stop) {}
+  SpecifierResult(const char *start,
+                  const T &fs)
+  : FS(fs), Start(start), Stop(false) {}
+
+  const char *getStart() const { return Start; }
+  bool shouldStop() const { return Stop; }
+  bool hasValue() const { return Start != nullptr; }
+  const T &getValue() const {
+    assert(hasValue());
+    return FS;
+  }
+  const T &getValue() { return FS; }
+};
+
+} // end analyze_format_string namespace
+} // end clang namespace
+
+#endif