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| -rw-r--r-- | doc/info/chap/error-reporting.texinfo | 53 | ||||
| -rw-r--r-- | doc/info/slibc.texinfo | 2 |
2 files changed, 55 insertions, 0 deletions
diff --git a/doc/info/chap/error-reporting.texinfo b/doc/info/chap/error-reporting.texinfo new file mode 100644 index 0000000..08571cd --- /dev/null +++ b/doc/info/chap/error-reporting.texinfo @@ -0,0 +1,53 @@ +@node Error reporting +@chapter Error reporting + +Many functions, especially those involving +system calls, detect and report exceptional +conditions, including error conditions and +interruptions. Exception conditions must often +be checked and handled, often by retrying, +doing something else, or reporting the error +to the user and exit. + +Unless otherwise specified, exceptional +conditions are reporting using the facilities +described in this chapter. + + +@menu +* Error checking:: Checking whether an exception condition occurred. +@end menu + + + +@node Error checking +@section Error checking + +@cpindex Checking for errors +@cpindex Errors checking +@cpindex Exception checking +Most functions return a sentinel value when an +exceptional condition occurs, typically a negative +value (actually @code{-1}), a constant such as +@code{EOF}, or @code{NULL}. This return value only +tells you that an exeception condition has occurred. + +@hfindex errno.h +@lvindex errno +By including the header file @file{<errno.h>}, the +modifiable lvalue @code{errno} is made available. +@sc{ISO}@tie{}C specifies that @code{errno} is not +necessarily a variable, but rather just an modifiable +lvalue. In fact, must @code{libc}:s, including +@code{slibc} defines it as a macro that calls a +function and uses the unary @code{*}-operator on the +return. + +@code{errno} is often thought of as a variable +declared as @code{int errno}, or @code{volatile int errno}. +But the value is thread-local, and is thus more +like @code{_Thread_local volatile int errno}. Because +of this, the @code{errno} is defined as a macro that +calls a function. Otherwise, it would not be implementable +without @sc{ISO}@tie{}C11. + diff --git a/doc/info/slibc.texinfo b/doc/info/slibc.texinfo index 8a57a2f..c13924e 100644 --- a/doc/info/slibc.texinfo +++ b/doc/info/slibc.texinfo @@ -292,6 +292,7 @@ Stockholm C Standard Library. @menu * Introduction:: Introduction to @command{slibc} and this manual. * Language facilities:: C language facilities provided by the library. +* Error reporting:: Detecting, reporting, and printing errors. * Free Software Needs Free Documentation:: Why free documentation is important. * GNU General Public License:: Copying and sharing @command{slibc}. @@ -312,6 +313,7 @@ Stockholm C Standard Library. @include chap/introduction.texinfo @include chap/language-facilities.texinfo +@include chap/error-reporting.texinfo |