Errata for The C Programming Language, Second Edition, by Brian Kernighanand Dennis Ritchie


I

Ioannis Vranos

Today I found out that the official page of errata for The C Programming Language, Second Edition, by Brian
Kernighan and Dennis Ritchie is down:

http://cm.bell-labs.com/cm/cs/cbook/2ediffs.html


I have mirrored the text of the official errata at my site:

http://www.cpp-software.net/documents/other_documents/2ediffs.html


I am also posting here these official errata for future reference:


----- Original errata text -----

Errata for The C Programming Language, Second Edition

This lists all known errors in The C Programming Language, Second Edition, by Brian Kernighan and Dennis
Ritchie (Prentice-Hall, 1988).

The pagination of the book has changed only in minor ways across printings of the English-language edition.
These errata now include section numbers, which are more likely to be preserved across translations. This
might help identify errors that survive into translated editions.



Changes between first and second printing:

The first printing of the book was made before the Standard was finalized; these copies say "Based on
Draft-Proposed ANSI C" on the front cover. All subsequent printings are identified by a large red ``ANSI C''
on the right center of the cover. Fortunately, the changes are minor; some repair our bugs, a few account for
last-minute changes in the draft standard. These changes were made so early that they probably do not apply to
you.

Two or three sentences in the Preface and Introduction are updated to describe the state of the Standard.

atof is in stdlib.h, not math.h; this changes pages 71(§4.2), 76(§4.2), 82(§4.7), 121(§5.11).

On page 86(§4.9), error corrected: missing automatic initializers are zero too.

On page 168(§7.8.7): changed 1 to 1.0 in frand example to avoid potential overflow.

Minor typos are corrected on pages 87(§4.10), 89(§4.11.12), 164(§7.6), 165)§7.7), 168(§7.8.7), 180(§8.6).

In particular, the comment on p. 180(§8.6) attached to st_ctime in the stat structure is repaired: "ctime"
stands for "change time" not "created time".

The inconspicuous references to noalias on pages 192(§A.2.4) and 211 or 212(§A8.2) are removed.

The following paragraph is added to the end of section A6.6 (page 199):

``A pointer may be converted to another pointer whose type is the same except for the addition or removal of
qualifiers (A4.4, A8.2) of the object type to which the pointer refers. If qualifiers are added, the new
pointer is equivalent to the old except for restrictions implied by the new qualifiers. If qualifiers are
removed, operations on the underlying object remain subject to the qualifiers in its actual declaration.''

On page 199, beginning of §A6.8, ``Any pointer may be converted to type void *...'' is changed to ``Any
pointer to an object may be converted to type void *...''.

On page 204, §A7.4.4, ``The operand of the unary + operator must have arithmetic or pointer type...'' should
read ``must have arithmetic type...''.

On page 206, §A7.9, about relational operators: ``Pointers to objects of the same type may be compared...'' is
changed to ``Pointers to object of the same type (ignoring any qualifiers) may be compared...''.

The indented material on page 209(§A7.17), ``According to the restrictions... relaxing it.'' is removed. [This
is related to the paragraph added above. The wording of the penultimate draft made it useless to take an (int
*) pointer, cast it to (const int *), then cast it back to (int *).]

On page 219 middle (§A8.7), initialization of structures, add ``Unnamed bit-field members are ignored, and are
not initialized.''

Appendix B changes:

p 242(§B1.1): Add ``fflush(NULL) flushes all output streams.'' to fflush description.

p 243(§B1.1): Change to ``it must be called before reading, writing or any other operation'' in setvbuf
description.

p 249(§B.3): Add ``Comparison functions treat arguments as unsigned char arrays.'' to string.h description.

p 255(§B10): Change range of tm_sec to (0,61) for leap seconds.

p 255(§B.10): Change CLK_TCK to CLOCKS_PER_SEC.

p 257(§B11): Drop U and L suffixes from limits.h constants. tm_sec range is (0,61) here too (§B10).

Appendix C change:

p 261(§C): Change ``External declarations without any specifiers...'' to ``External data declarations without
any specifiers...''.

The index has been reprinted to fix a couple of typos and account for motion within Appendix A; one page of
the table of contents is changed.

A later printing in October, 1989, made minor changes on page 131(§6.2) to add & to the last example ( struct
rect r, *rp = &r;), on page 208(§A.17) to change ``equal'' to ``unequal'' in the description of logical OR,
and on page 254(§B.8) to clarify that for automatics variables, only those declared volatile are restored to
their latest values after a setjmp / longjmp sequence.




Errors not corrected in any printing:

The following errors have not yet been fixed in any printing.

41(§2.6): The loop at the bottom of the page is functionally equivalent to the one on page 29(§1.9), but not
identical in form, as is implied by the text.

44(§2.7): 1U is an unsigned int, not an int.

49(§2.9): In the discussion of shift operators, `which must be positive' should be `which must be non-negative'.

53(§2.12): The note under the table should say & as well as + - * has higher precedence as a unary operator.

102(§5.4): NULL is standardly defined in <stddef.h>, although it also appears in several other headers like
<stdio.h> and <stdlib.h>.

111(§5.7): Indent is too large, and a bit of the month_day program text is cut off.

114(§5.9): quote missing in "Jan, near top of page.

117(§5.10): In the find example, the program increments argv[0]. This is not specifically forbidden, but not
specifically allowed either.

119-121(§5.11): The qsort discussion needs recasting in several ways. First, qsort is a standard routine in
ANSI/ISO C, so the rendition here should be given a different name, especially because the arguments to
standard qsort are a bit different: the standard accepts a base pointer and a count, while this example uses a
base pointer and two offsets.

Also, the comparison-routine argument is not treated well. The call shown on p 119, with an argument

(int (*)(void*,void*))(numeric? numcmp : strcmp)

is not only complicated, but only barely passes muster. Both numcmp and strcmp take char * arguments, but this
expression casts pointers to these functions to a function pointer that takes void * arguments. The standard
does say that void * and char * have the same representation, so the example will almost certainly work in
practice, and is at least defensible under the standard. There are too many lessons in these pages.

136(§6.3) The getword function can overflow word by one character. A sufficient fix is to test '--lim>1'
instead of '>0' in the for loop.

142(§6.5, toward the end): The remark about casting the return value of malloc ("the proper method is to
declare ... then explicitly coerce") needs to be rewritten. The example is correct and works, but the advice
is debatable in the context of the 1988-1989 ANSI/ISO standards. It's not necessary (given that coercion of
void * to ALMOSTANYTYPE * is automatic), and possibly harmful if malloc, or a proxy for it, fails to be
declared as returning void *. The explicit cast can cover up an unintended error. On the other hand, pre-ANSI,
the cast was necessary, and it is in C++ also.

143(§6.5): strdup is not indexed.

154(§7.2) table 7-1: arguments corresponding to o, x, X, u should be described as unsigned int.

158(§7.4) table 7-2: type of arguments corresponding to o, x should be unsigned int *.

164,165(§7.7): (text and code) fputs returns EOF on error, non-negative for OK.

165(§7.7): The comment at the beginning of the fgets example, "get at most n chars" would be better written
"get at most n-1 chars, plus a null".

167(§7.8.5): [the return value of malloc or calloc] "must be cast into the appropriate type" is incorrect as
stated. See the remarks just above for p. 142.

176-178(§8.5): OPEN_MAX is used to define the largest number of simultaneously open files in the example
stdio.h; the ANSI/ISO name for this is instead FOPEN_MAX.

187-188(&sect8.7): malloc and the accompanying routine morecore are not presented as a whole program, and the
routines should be OK, but moving the declaration
static Header *morecore(unsigned);
to file scope (instead of inside malloc) would be a better way to make sure scope and linkage issues are
handled properly.

193(§A.2.5.1): If an integer constant is suffixed with UL, it is unsigned long.

195(§A4): To the list at the start of the section, "Identifiers, or names, refer to a variety of things...",
add labels as well.

195(§A4.1) The first few sentences might be reworded a bit to emphasize that there is a distinction between
storage duration and scope, though both are influenced by explicit and implicit storage-class specifiers.

197(§A5): "An object is a named region of storage..." should read "named or pointed-to region..."

200(§ A7.1): The actual list of operators that prevent the conversion of arrays into pointers is just & and
sizeof, not the various assignment operators. In practice this is not important, because arrays (converted or
not) cannot be assigned to for other reasons.

207 (§A7.10): add to first paragraph: equality operators on pointers may also be applied to pointers to
different objects.

229(§A12.3), 239(§A13): Syntax: the argument list is optional (can be empty) in macro definitions with
parentheses.

231(§A12.3): Extra right parenthesis in nested call to cat macro.

232(§A12.5): The result of the defined operator is not replaced literally by 0L or 1L, nor are undefined names
literally by 0L, but just by plain 0 or 1. However, the constant expression is nevertheless evaluated as if
these and other constants appearing have long or unsigned long type.

232(§A12.5), likewise on p. 239(§A13), in the sections on the pseudo-grammar of the preprocessor, the productions

preprocessor-conditional:
if-line text elif-parts else-part_opt # endif

elif-parts:
elif-line text
elif-parts_opt

should be written

preprocessor-conditional:
if-line text elif-parts_opt else-part_opt # endif

elif-parts:
elif-line text elif-parts_opt

244(§B1.2): In table B-1, the argument corresponding to o, u, x, X is unsigned int.

245(§B1.2): vprintf, vfprintf, vsprintf return int.

245(§B1.3, and also at p. 157 §7.4): The scanf functions do not ignore white space in formats; if white space
occurs at a place in the format, any white space in the corresponding input is skipped.

246(§B1.3): In table B-2, arguments corresponding to o, x, X, u are unsigned int *.

246(§B1.3): First argument of sscanf should have type const char *.

249(§B3): In the description of strncpy, t should be ct.

210(§A8.1): It is said that a register object cannot have the & operator applied `explicitly or implicitly,'
which is true, but needs an amplifying clause to show that the implicit & comes from mention of an array name,
so declaring an array as a register is fruitless.

There is no mention of the offsetof macro in §B.

257,258(§B11): In the definitions of both FLT_MAX_EXP and DBL_MAX_EXP, the expression FLT_RADIX^n - 1 should
be written FLT_RADIX^(n-1).

Index: stddef.h is listed but not summarized in the text; It needs a section in Appendix B.

char, double, long, short are on page 9, not page 10. sizeof is on 242, not 247. ``byte'' is not indexed.
size_t does occur on p. 247 in declarations.



Updated Oct 23 2006 with program bug on line 136

Copyright © 2002 Lucent Technologies. All rights reserved.



----- End of original errata text -----




--
Ioannis A. Vranos

C95 / C++03 Developer

http://www.cpp-software.net
 
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I

Ioannis Vranos

My solution suggestions, for ambiguous errata solutions of the above official errata:



I sent via email the following to DMR and BWK, on April 2008:


Dear Mr. Brian Kernighan and Mr. Dennis Ritchie,

At the errata page of "The C Programming Language" 2nd Edition
(<http://www-db-out.research.bell-labs.com/cm/cs/cbook/2ediffs.html>),
most of the errata are of the style "On page xyz, section abc, replace
this with this" or "On page xyz, section abc, add this to this".


However there are some errata that I call "ambiguous", about which there
is not a suggested specific action for fixing the errors/omissions.

So I am sending to you some proposed solutions for these, that I made,
based strictly on their errata comments.


These proposed solutions are to be added to the errata page exactly as
they appear after the phrase "Proposed solution:", replacing their
"ambiguous" corresponding text.




1. "119-121(§5.11): The qsort discussion needs recasting in several
ways. First, qsort is a standard routine in ANSI/ISO C, so the rendition
here should be given a different name, especially because the arguments
to standard qsort are a bit different: the standard accepts a base
pointer and a count, while this example uses a base pointer and two
offsets".


Proposed solution:

Rename the "qsort" references, declarations, definitions and calls, as
"sort" in the entire section 5.11.



2. "Also, the comparison-routine argument is not treated well. The call
shown on p 119, with an argument

(int (*)(void*,void*))(numeric? numcmp : strcmp)

is not only complicated, but only barely passes muster. Both numcmp and
strcmp take char * arguments, but this expression casts pointers to
these functions to a function pointer that takes void * arguments. The
standard does say that void * and char * have the same representation,
so the example will almost certainly work in practice, and is at least
defensible under the standard. There are too many lessons in these pages".


Proposed solution:

At the bottom of the page 119 (section 5.11), a note should be added:

"Note: In main(), the call with an argument (int
(*)(void*,void*))(numeric? numcmp : strcmp) is not only complicated, but
only barely passes muster. Both numcmp and strcmp take char * arguments,
but this expression casts pointers to these functions to a function
pointer that takes void * arguments. The standard does say that void *
and char * have the same representation, so the example will almost
certainly work in practice, and is at least defensible under the standard".



3. "195(§A4.1) The first few sentences might be reworded a bit to
emphasize that there is a distinction between storage duration and
scope, though both are influenced by explicit and implicit storage-class
specifiers".


Proposed solution:

Right after the sentence of A4.1, "Several keywords, together with the
context of an object's declaration, specify its storage class", the
following sentence should be added:

"There is a distinction between storage duration and scope, though both
are influenced by explicit and implicit storage-class specifiers".



4. "245(§B1.3, and also at p. 157 §7.4): The scanf functions do not
ignore white space in formats; if white space occurs at a place in the
format, any white space in the corresponding input is skipped".


Proposed solution:

On page 157 (7.4) and on page 245 (B1.3), the first sentence with a *
(dot), should be replaced with the sentence:

"* If white space occurs at a place in the format, any white space in
the corresponding input is skipped".



5. "210(§A8.1): It is said that a register object cannot have the &
operator applied `explicitly or implicitly,' which is true, but needs an
amplifying clause to show that the implicit & comes from mention of an
array name, so declaring an array as a register is fruitless".


Proposed solution:

On page 210 (A8.1), after the sentence "However, if an object is
declared register, the unary & operator may not be applied to it,
explicitly or implicitly", the following sentence should be added:

"The implicit & comes from mention of an array name, so declaring an
array as a register is fruitless".



6. "There is no mention of the offsetof macro in B".

"Index: stddef.h is listed but not summarized in the text; It needs a
section in Appendix B".


Proposed solution:

At the end of Appendix B (page 258), the following should be added:

"B12. Common standard type definitions: <stddef.h>

The header <stddef.h> defines the following types and macros:

The types are:

ptrdiff_t
A signed integral type of the result of subtracting two pointers.

wchar_t
An integral type whose range of values can represent distinct
wide-character codes for all members of the largest extended character
set specified among the supported locales; the null character has the
code value 0 and each member of the basic character set has a code value
equal to its value when used as the lone character in an integer
character constant.

size_t
An unsigned integral type of the result of the sizeof operator.


The macros are:

NULL
NULL expands to an implementation-defined null pointer constant.

offsetof(type, member-designator)
offsetof expands to an integral constant expression of type size_t,
the value of which is the offset in bytes to the structure member
(member-designator), from the beginning of its structure (type)".


Also a reference to offsetof should be added in the INDEX section (page
268), and the page number 258 should be added to the reference of
<stddef.h> header, in the INDEX section (page 270).


Copyright (C) 2008 Ioannis Vranos




--
Ioannis A. Vranos

C95 / C++03 Developer

http://www.cpp-software.net
 
I

Ioannis Vranos

==> Encoding of this text: Unicode (UTF-8).



My solution suggestions, for ambiguous errata solutions of the above official errata:



I sent via email the following to DMR and BWK, on April 2008:


Dear Mr. Brian Kernighan and Mr. Dennis Ritchie,

At the errata page of "The C Programming Language" 2nd Edition
(<http://www-db-out.research.bell-labs.com/cm/cs/cbook/2ediffs.html>),
most of the errata are of the style "On page xyz, section abc, replace
this with this" or "On page xyz, section abc, add this to this".


However there are some errata that I call "ambiguous", about which there
is not a suggested specific action for fixing the errors/omissions.

So I am sending to you some proposed solutions for these, that I made,
based strictly on their errata comments.


These proposed solutions are to be added to the errata page exactly as
they appear after the phrase "Proposed solution:", replacing their
"ambiguous" corresponding text.




1. "119-121(§5.11): The qsort discussion needs recasting in several
ways. First, qsort is a standard routine in ANSI/ISO C, so the rendition
here should be given a different name, especially because the arguments
to standard qsort are a bit different: the standard accepts a base
pointer and a count, while this example uses a base pointer and two
offsets".


Proposed solution:

Rename the "qsort" references, declarations, definitions and calls, as
"sort" in the entire section 5.11.



2. "Also, the comparison-routine argument is not treated well. The call
shown on p 119, with an argument

(int (*)(void*,void*))(numeric? numcmp : strcmp)

is not only complicated, but only barely passes muster. Both numcmp and
strcmp take char * arguments, but this expression casts pointers to
these functions to a function pointer that takes void * arguments. The
standard does say that void * and char * have the same representation,
so the example will almost certainly work in practice, and is at least
defensible under the standard. There are too many lessons in these pages".


Proposed solution:

At the bottom of the page 119 (section 5.11), a note should be added:

"Note: In main(), the call with an argument (int
(*)(void*,void*))(numeric? numcmp : strcmp) is not only complicated, but
only barely passes muster. Both numcmp and strcmp take char * arguments,
but this expression casts pointers to these functions to a function
pointer that takes void * arguments. The standard does say that void *
and char * have the same representation, so the example will almost
certainly work in practice, and is at least defensible under the standard".



3. "195(§A4.1) The first few sentences might be reworded a bit to
emphasize that there is a distinction between storage duration and
scope, though both are influenced by explicit and implicit storage-class
specifiers".


Proposed solution:

Right after the sentence of A4.1, "Several keywords, together with the
context of an object's declaration, specify its storage class", the
following sentence should be added:

"There is a distinction between storage duration and scope, though both
are influenced by explicit and implicit storage-class specifiers".



4. "245(§B1.3, and also at p. 157 §7.4): The scanf functions do not
ignore white space in formats; if white space occurs at a place in the
format, any white space in the corresponding input is skipped".


Proposed solution:

On page 157 (7.4) and on page 245 (B1.3), the first sentence with a *
(dot), should be replaced with the sentence:

"* If white space occurs at a place in the format, any white space in
the corresponding input is skipped".



5. "210(§A8.1): It is said that a register object cannot have the &
operator applied `explicitly or implicitly,' which is true, but needs an
amplifying clause to show that the implicit & comes from mention of an
array name, so declaring an array as a register is fruitless".


Proposed solution:

On page 210 (A8.1), after the sentence "However, if an object is
declared register, the unary & operator may not be applied to it,
explicitly or implicitly", the following sentence should be added:

"The implicit & comes from mention of an array name, so declaring an
array as a register is fruitless".



6. "There is no mention of the offsetof macro in B".

"Index: stddef.h is listed but not summarized in the text; It needs a
section in Appendix B".


Proposed solution:

At the end of Appendix B (page 258), the following should be added:

"B12. Common standard type definitions: <stddef.h>

The header <stddef.h> defines the following types and macros:

The types are:

ptrdiff_t
A signed integral type of the result of subtracting two pointers.

wchar_t
An integral type whose range of values can represent distinct
wide-character codes for all members of the largest extended character
set specified among the supported locales; the null character has the
code value 0 and each member of the basic character set has a code value
equal to its value when used as the lone character in an integer
character constant.

size_t
An unsigned integral type of the result of the sizeof operator.


The macros are:

NULL
NULL expands to an implementation-defined null pointer constant.

offsetof(type, member-designator)
offsetof expands to an integral constant expression of type size_t,
the value of which is the offset in bytes to the structure member
(member-designator), from the beginning of its structure (type)".


Also a reference to offsetof should be added in the INDEX section (page
268), and the page number 258 should be added to the reference of
<stddef.h> header, in the INDEX section (page 270).


Copyright (C) 2008 Ioannis Vranos
 
K

Keith Thompson

Ioannis Vranos said:
Today I found out that the official page of errata for The C
Programming Language, Second Edition, by Brian Kernighan and Dennis
Ritchie is down:

http://cm.bell-labs.com/cm/cs/cbook/2ediffs.html


I have mirrored the text of the official errata at my site:

http://www.cpp-software.net/documents/other_documents/2ediffs.html


I am also posting here these official errata for future reference:
[snip]

I've noticed that that web page seems to be down fairly often. It
will probably be back up again before long.

If you're going to mirror it (and thanks for doing do), I suggest
adding header text with a link to the original site and the date it
was last updated, and the date you last copied it. <OT>For most web
pages, you can determine when the page itself was last updated using
"curl --head url".</OT> I'd mention both this and the date when it was
last copied.
 
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I

Ioannis Vranos

Keith said:
Ioannis Vranos said:
Today I found out that the official page of errata for The C
Programming Language, Second Edition, by Brian Kernighan and Dennis
Ritchie is down:

http://cm.bell-labs.com/cm/cs/cbook/2ediffs.html


I have mirrored the text of the official errata at my site:

http://www.cpp-software.net/documents/other_documents/2ediffs.html


I am also posting here these official errata for future reference:
[snip]

I've noticed that that web page seems to be down fairly often. It
will probably be back up again before long.

If you're going to mirror it (and thanks for doing do), I suggest
adding header text with a link to the original site and the date it
was last updated, and the date you last copied it.


OK, I did these.

The date when the original page that was mirrored was modified, is already mentioned at the end of the document.




--
Ioannis A. Vranos

C95 / C++03 Developer

http://www.cpp-software.net
 

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