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Re: bug in optimised strstr

Jeff Johnston wrote:
Eric Blake wrote:
Jeff Johnston <jjohnstn <at>> writes:

  max_suffix = SIZE_MAX;
  j = 0;
  k = p = 1;
  while (j + k < needle_len)
      a = CANON_ELEMENT (needle[j + k]);
      b = CANON_ELEMENT (needle[max_suffix + k]);

it is the line b=....

It cannot be correct as you are trying to reference SIZE_MAX + 1 the first time through the loop.

But the comments state:

/* Invariants:
0 <= j < NEEDLE_LEN - 1
-1 <= max_suffix{,_rev} < j (treating SIZE_MAX as if it were signed)

On cygwin, this works (in other words, I'm not reproducing the crash). The intent is that this line is referencing needle[0]. What type is size_t on your platform, and the value of SIZE_MAX? Could it be that there is some type promotion going on, where the result of SIZE_MAX+1 results in a 64-bit type containing 2**32 instead of 0, as is required by modulo math since size_t is unsigned?

Ok, I got mixed up on what SIZE_MAX was supposed to be. For x86, stdint.h is being overridden with one in libc/sys/linux/include that has a wrong value for SIZE_MAX (LONG_MAX). I am rebuilding now. I can't say what is happening for arm since it should be using the same stdint.h from libc/include.

-- Jeff J.

Patch works for x86-linux and is checked in. I don't have an arm system to play around with. Sam, are you running arm-linux (which isn't in newlib)? That would use the code in question. Otherwise, can you provide more details (e.g. run under gdb and print out the various information above)?

-- Jeff J.

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