| Number | 636
|
| Category | errata
|
| Synopsis | 4.2.3.2 et al: null character is "NUL", not "NULL"
|
| State | lrmdraft
|
| Class | errata-simple
|
| Arrival-Date | Nov 24 2004
|
| Originator | Shalom Bresticker <Shalom.Bresticker@freescale.com>
|
| Release | 2001b
|
| Description |
Steven Dovich said in http://www.eda.org/sv-cc/hm/2205.html: "To be properly consistent with the C language, we also need to recognize that NULL is not a character, it is a pointer. C strings are composed of characters and are terminated by a "null character". Common usage also designates the character valued as '\0' as the NUL character from the ASCII character names (note the three letter spelling). " and 2207.html: "Yes, though as I noted, NUL as a character name is not acknowledged in the C standard. It is a (somewhat) common usage from the ASCII standard and is replaced in the C standard with "null character". When spelled in lower case, the word "null" is ambiguous and must be qualified by "character", "pointer", etc. The upper case NULL is the standardized spelling for a "null pointer", a constant expression evaluating to zero that is used as a pointer. /sjd > So NULL is a pointer and NUL is a character?" and Brad Pierce in http://www.eda.org/sv-ec/hm/2220.html: "In ANSI C, NULL is a macro that the C preprocessor converts into a null pointer constant. A null pointer constant is an integer constant expression with the value 0 or the cast of such an expression to void*. However, it is NOT a null pointer. It is compiled into a null pointer. And the bit representation of a null pointer need NOT be zeros. Null pointers are implementation-dependent and may be different for different types, for example, pointers to data objects vs. pointers to functions. All that's required is that any two null pointers are ==, that casting a null pointer of one type to another pointer type results in a null pointer, and that null pointers can't be confused for an actual pointer to some object or function." What is relevant to this errata submission is that when referring to null characters, it should refer to NUL instead of NULL. Places I found where this apparently should be changed are: 4.2.3.2: "The comparison and concatenation operators shall not distinguish between zeros resulting from padding and the original string characters (\0, ASCII NULL)." 4.2.3.3: The null string ("") shall be considered equivalent to the ASCII NULL ("\0") which has a value zero (0), which is different from a string "0". In 27.15, I am confused by the use of both the terms "character array" and "array of pointers to characters": "The format of the argv array is that each pointer in the array shall point to a NULL terminated character array which contains the string located on the tool's invocation command line. There shall be `argc' entries in the argv array. The value in entry zero shall be the tool's name. The vendor tool may provide a command line option to pass a file containing a set of options. In that case, the argument strings returned by vpi_get_vlog_info() shall contain the vendor option string name followed by a pointer to a NULL terminated array of pointers to characters. This new array shall contain the parsed contents of the file. The value in entry zero shall contain the name of the file. The remaining entries shall contain pointers to NULL terminated character arrays containing the different options in the file. The last entry in this array shall be NULL. If one of the options is the vendor file option, then the next pointer shall behave the same as described above. " -- Shalom Bresticker Shalom.Bresticker @freescale.com Design & Verification Methodology Tel: +972 9 9522268 Freescale Semiconductor Israel, Ltd. Fax: +972 9 9522890 POB 2208, Herzlia 46120, ISRAEL Cell: +972 50 5441478 [ ]Freescale Internal Use Only [ ]Freescale Confidential Proprietary |
| Fix |
CHANGE "NULL" to "NUL" in 4.2.3.2: "The comparison and concatenation operators shall not distinguish between zeros resulting from padding and the original string characters (\0, ASCII NULL)." 4.2.3.3: The null string ("") shall be considered equivalent to the ASCII NULL ("\0") which has a value zero (0), which is different from a string "0". 27.15: "The format of the argv array is that each pointer in the array shall point to a NULL terminated character array which contains the string located on the tool's invocation command line." 27.15: "The remaining entries shall contain pointers to NULL terminated character arrays containing the different options in the file." |
| Audit-Trail |
From: Steven Sharp <sharp@cadence.com> To: etf-bugs@boyd.com, Shalom.Bresticker@freescale.com Cc: Subject: Re: errata/636: 4.2.3.2 et al: null character is "NUL", not "NULL" Date: Wed, 24 Nov 2004 13:25:53 -0500 (EST) >In 27.15, I am confused by the use of both the terms "character array" and >"array of pointers to characters": I think it involves both. There is an array of pointers, with the last pointer in the array being a NULL pointer, as a terminator. Each of those pointers points to an array of characters, with the last character in each being a NUL character, as a terminator. This allows for an arbitrary number of command line arguments, each of which is an arbitrary length string. Steven Sharp sharp@cadence.com Fix replaced by Shalom.Bresticker@freescale.com on Thu Nov 25 00:08:03 2004 CHANGE "NULL" to "NUL" in 4.2.3.2: "The comparison and concatenation operators shall not distinguish between zeros resulting from padding and the original string characters (\0, ASCII NULL)." 4.2.3.3: The null string ("") shall be considered equivalent to the ASCII NULL ("\0") which has a value zero (0), which is different from a string "0". 27.15: "The remaining entries shall contain pointers to NULL terminated character arrays containing the different options in the file." Fix replaced by Shalom.Bresticker@freescale.com on Mon Nov 29 09:46:00 2004 CHANGE "NULL" to "NUL" in 4.2.3.2: "The comparison and concatenation operators shall not distinguish between zeros resulting from padding and the original string characters (\0, ASCII NULL)." 4.2.3.3: The null string ("") shall be considered equivalent to the ASCII NULL ("\0") which has a value zero (0), which is different from a string "0". 27.15: "The format of the argv array is that each pointer in the array shall point to a NULL terminated character array which contains the string located on the tool's invocation command line." 27.15: "The remaining entries shall contain pointers to NULL terminated character arrays containing the different options in the file." |
| Unformatted |
|
Hosted by Boyd Technology