[llvm-commits] [llvm] r79065 - /llvm/trunk/lib/Support/FormattedStream.cpp

[Dan Gohman]

On Aug 17, 2009, at 2:42 AM, Artur Pietrek <pietreka at gmail.com> wrote:

>
>
> On Sat, Aug 15, 2009 at 4:02 AM, Dan Gohman <gohman at apple.com> wrote:
>
> -/// ComputeColumn - Examine the current output and figure out which
> +/// CountColumns - Examine the given char sequence and figure out  
> which
>  /// column we end up in after output.
>  ///
> -void formatted_raw_ostream::ComputeColumn() {
> +static unsigned CountColumns(unsigned Column, const char *Ptr,  
> size_t Size) {
>   // Keep track of the current column by scanning the string for
>   // special characters
>
> -  // The buffer may have been allocated underneath us.
> -  if (Scanned == 0 && GetNumBytesInBuffer() != 0) {
> -    Scanned = begin();
> -  }
> -
> -  while (Scanned != end()) {
> -    ++ColumnScanned;
> -    if (*Scanned == '\n' || *Scanned == '\r')
> -      ColumnScanned = 0;
> -    else if (*Scanned == '\t')
> +  for (const char *End = Ptr + Size; Ptr != End; ++Ptr) {
> +    ++Column;
> +    if (*Ptr == '\n' || *Ptr == '\r')
> +      Column = 0;
> +    else if (*Ptr == '\t')
>       // Assumes tab stop = 8 characters.
> -      ColumnScanned += (8 - (ColumnScanned & 0x7)) & 0x7;
> -    ++Scanned;
> +      Column += (8 - (Column & 0x7)) & 0x7;
>   }
> +
> +  return Column;
> +}
>
> Hi all,
>
> Is it legal to output Instruction or any Value using formatted  
> stream like this:
> Out << *Instr;

Yes, that's fine.  Fairly common, in fact.

>
> I was using it to print commented LLVM instructions to my assembly  
> to check if I'm translating instructions correctly, but since the  
> change above I get segfault after running my backend.
>
> Changing line:
> for (const char *End = Ptr + Size; Ptr != End; ++Ptr) {
>
> to:
> +  for (const char *End = Ptr + Size; Ptr < End; ++Ptr) {
>
> helps. Is it bug or I just should not use it that way?

The change shouldn't be necessary.  It sounds like there's a bug.  Is  
Ptr pointing to a valid string when this happens?

Dan

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