Change raw_ostream so that it doesn't call llvm_report_error

immediately on every output error. Instead, add a flag to
raw_ostream, and set the flag whenever an error is detected.

The flag can be queried and cleared from the public API. This
gives applications more flexibility to handling errors in
application-specific ways.

If the flag is not cleared when the raw_ostream is destructed,
llvm_report_error is called from the destructor. This ensures
that errors are not implicitly silenced, and provides
convenient default behavior for tools like llc and opt.
Clients wishing to avoid llvm_report_error calls from
raw_ostream should check for errors and clear the error flag.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@75857 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 45 insertions, 12 deletions

diff --git a/include/llvm/Support/raw_ostream.h b/include/llvm/Support/raw_ostream.h
index 2cf9d22..367c35c 100644
--- a/include/llvm/Support/raw_ostream.h
+++ b/include/llvm/Support/raw_ostream.h
@@ -44,6 +44,10 @@ private:
   char *OutBufStart, *OutBufEnd, *OutBufCur;
   bool Unbuffered;
 
+  /// Error This flag is true if an error of any kind has been detected.
+  ///
+  bool Error;
+
 public:
   // color order matches ANSI escape sequence, don't change
   enum Colors {
@@ -58,18 +62,31 @@ public:
     SAVEDCOLOR
   };
 
-  explicit raw_ostream(bool unbuffered=false) : Unbuffered(unbuffered) {
+  explicit raw_ostream(bool unbuffered=false)
+    : Unbuffered(unbuffered), Error(false) {
     // Start out ready to flush.
     OutBufStart = OutBufEnd = OutBufCur = 0;
   }
 
-  virtual ~raw_ostream() {
-    delete [] OutBufStart;
-  }
+  virtual ~raw_ostream();
 
   /// tell - Return the current offset with the file.
   uint64_t tell() { return current_pos() + GetNumBytesInBuffer(); }
 
+  /// has_error - Return the value of the flag in this raw_ostream indicating
+  /// whether an output error has been encountered.
+  bool has_error() const {
+    return Error;
+  };
+
+  /// clear_error - Set the flag read by has_error() to false. If the error
+  /// flag is set at the time when this raw_ostream's destructor is called,
+  /// llvm_report_error is called to report the error. Use clear_error()
+  /// after handling the error to avoid this behavior.
+  void clear_error() {
+    Error = false;
+  };
+
   //===--------------------------------------------------------------------===//
   // Configuration Interface
   //===--------------------------------------------------------------------===//
@@ -213,6 +230,11 @@ private:
   /// counting the bytes currently in the buffer.
   virtual uint64_t current_pos() = 0;
 
+protected:
+  /// error_detected - Set the flag indicating that an output error has
+  /// been encountered.
+  void error_detected() { Error = true; }
+
   //===--------------------------------------------------------------------===//
   // Private Interface
   //===--------------------------------------------------------------------===//
@@ -311,8 +333,8 @@ raw_ostream &errs();
 //===----------------------------------------------------------------------===//
 
 /// raw_os_ostream - A raw_ostream that writes to an std::ostream.  This is a
-/// simple adaptor class.  It does not check for I/O errors; clients should use
-/// the underlying stream to detect errors.
+/// simple adaptor class.  It does not check for output errors; clients should
+/// use the underlying stream to detect errors.
 class raw_os_ostream : public raw_ostream {
   std::ostream &OS;
 
@@ -332,7 +354,7 @@ public:
 };
 
 /// raw_string_ostream - A raw_ostream that writes to an std::string.  This is a
-/// simple adaptor class.
+/// simple adaptor class. This class does not encounter output errors.
 class raw_string_ostream : public raw_ostream {
   std::string &OS;
 
@@ -358,7 +380,8 @@ public:
 };
 
 /// raw_svector_ostream - A raw_ostream that writes to an SmallVector or
-/// SmallString.  This is a simple adaptor class.
+/// SmallString.  This is a simple adaptor class. This class does not
+/// encounter output errors.
 class raw_svector_ostream : public raw_ostream {
   SmallVectorImpl<char> &OS;
 
diff --git a/lib/Support/raw_ostream.cpp b/lib/Support/raw_ostream.cpp
index b13d922..8724801 100644
--- a/lib/Support/raw_ostream.cpp
+++ b/lib/Support/raw_ostream.cpp
@@ -44,6 +44,16 @@
 
 using namespace llvm;
 
+raw_ostream::~raw_ostream() {
+  delete [] OutBufStart;
+
+  // If there are any pending errors, report them now. Clients wishing
+  // to avoid llvm_report_error calls should check for errors with
+  // has_error() and clear the error flag with clear_error() before
+  // destructing raw_ostream objects which may have errors.
+  if (Error)
+    llvm_report_error("IO failure on output stream.");
+}
 
 // An out of line virtual method to provide a home for the class vtable.
 void raw_ostream::handle() {}
@@ -282,7 +292,7 @@ raw_fd_ostream::~raw_fd_ostream() {
     flush();
     if (ShouldClose)
       if (::close(FD) != 0)
-        llvm_report_error("IO failure closing output stream.");
+        error_detected();
   }
 }
 
@@ -290,7 +300,7 @@ void raw_fd_ostream::write_impl(const char *Ptr, unsigned Size) {
   assert (FD >= 0 && "File already closed.");
   pos += Size;
   if (::write(FD, Ptr, Size) != (ssize_t) Size)
-    llvm_report_error("IO failure writing to output stream.");
+    error_detected();
 }
 
 void raw_fd_ostream::close() {
@@ -298,7 +308,7 @@ void raw_fd_ostream::close() {
   ShouldClose = false;
   flush();
   if (::close(FD) != 0)
-    llvm_report_error("IO failure closing output stream.");
+    error_detected();
   FD = -1;
 }
 
@@ -306,7 +316,7 @@ uint64_t raw_fd_ostream::seek(uint64_t off) {
   flush();
   pos = ::lseek(FD, off, SEEK_SET);
   if (pos != off)
-    llvm_report_error("IO failure seeking on output stream.");
+    error_detected();
   return pos;  
 }