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Re: [RFC PATCH 6/6] utf8.c: avoid char overflow

From
Johannes Schindelin <johannes.schindelin@gmx.de>
Date
Jul 9, 2018, 13:14 UTC
Message-ID
<nycvar.QRO.7.76.6.1807091513130.75@tvgsbejvaqbjf.bet>
In-Reply-To
<20180708144342.11922-7-dev+git@drbeat.li>
Hi Beat,
On Sun, 8 Jul 2018, Beat Bolli wrote:
Show 30 quoted lines
> In ISO C, char constants must be in the range -128..127. Change the BOM
> constants to unsigned char to avoid overflow.
> 
> Signed-off-by: Beat Bolli <dev+git@drbeat.li>
> ---
>  utf8.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/utf8.c b/utf8.c
> index d55e20c641..833ce00617 100644
> --- a/utf8.c
> +++ b/utf8.c
> @@ -561,15 +561,15 @@ char *reencode_string_len(const char *in, int insz,
>  #endif
>  
>  static int has_bom_prefix(const char *data, size_t len,
> -			  const char *bom, size_t bom_len)
> +			  const unsigned char *bom, size_t bom_len)
>  {
>  	return data && bom && (len >= bom_len) && !memcmp(data, bom, bom_len);
>  }
>  
> -static const char utf16_be_bom[] = {0xFE, 0xFF};
> -static const char utf16_le_bom[] = {0xFF, 0xFE};
> -static const char utf32_be_bom[] = {0x00, 0x00, 0xFE, 0xFF};
> -static const char utf32_le_bom[] = {0xFF, 0xFE, 0x00, 0x00};
> +static const unsigned char utf16_be_bom[] = {0xFE, 0xFF};
> +static const unsigned char utf16_le_bom[] = {0xFF, 0xFE};
> +static const unsigned char utf32_be_bom[] = {0x00, 0x00, 0xFE, 0xFF};
> +static const unsigned char utf32_le_bom[] = {0xFF, 0xFE, 0x00, 0x00};

An alternative approach that might be easier to read (and avoids the confusion arising from our use of (signed) chars for strings pretty much everywhere):

#define FE ((char)0xfe) #define FF ((char)0xff)

...

Ciao, Dscho

Previous: Beat BolliNext: Beat Bolli
Message 14 of 39 in “Compile cleanly in pedantic mode”
  1. 0/6 Compile cleanly in pedantic modeBeat Bolli, Jul 8, 2018
  2. 4/6 sequencer.c: avoid empty statements at top levelBeat Bolli, Jul 8, 2018
  3. Eric SunshineJul 8, 2018
  4. Philip OakleyJul 8, 2018
  5. ig@drbeat.liJul 9, 2018
  6. Junio C HamanoJul 9, 2018
  7. Beat BolliJul 9, 2018
  8. 2/6 refs/refs-internal.h: avoid forward declaration of an enumBeat Bolli, Jul 8, 2018
  9. Jeff KingJul 9, 2018
  10. Beat BolliJul 9, 2018
  11. Jeff KingJul 10, 2018
  12. 3/6 convert.c: replace "\e" escapes with "\033".Beat Bolli, Jul 8, 2018
  13. 6/6 utf8.c: avoid char overflowBeat Bolli, Jul 8, 2018
  14. Johannes SchindelinJul 9, 2018
  15. Beat BolliJul 9, 2018
  16. Beat BolliJul 9, 2018
  17. Junio C HamanoJul 9, 2018
  18. Beat BolliJul 9, 2018
  19. Junio C HamanoJul 9, 2018
  20. Johannes SchindelinJul 9, 2018
  21. 1/6 connect.h: avoid forward declaration of an enumBeat Bolli, Jul 8, 2018
  22. 5/6 string-list.c: avoid conversion from void * to function pointerBeat Bolli, Jul 8, 2018
  23. Johannes SchindelinJul 9, 2018
  24. Junio C HamanoJul 9, 2018
  25. 0/6 Compile cleanly in pedantic modeBeat Bolli, Jul 9, 2018
  26. Beat BolliJul 9, 2018
  27. Junio C HamanoJul 9, 2018
  28. Beat BolliJul 9, 2018
  29. Beat BolliJul 10, 2018
  30. Junio C HamanoJul 11, 2018
  31. Johannes SchindelinJul 12, 2018
  32. Junio C HamanoJul 12, 2018
  33. 1/6 connect.h: avoid forward declaration of an enumBeat Bolli, Jul 9, 2018
  34. 5/6 string-list.c: avoid conversion from void * to function pointerBeat Bolli, Jul 9, 2018
  35. 3/6 convert.c: replace "\e" escapes with "\033".Beat Bolli, Jul 9, 2018
  36. 2/6 refs/refs-internal.h: avoid forward declaration of an enumBeat Bolli, Jul 9, 2018
  37. 6/6 utf8.c: avoid char overflowBeat Bolli, Jul 9, 2018
  38. 4/6 sequencer.c: avoid empty statements at top levelBeat Bolli, Jul 9, 2018
  39. Junio C HamanoJul 9, 2018

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