error, error_at_line, error_message_count, error_one_per_line, error_print_progname - glibc error reporting functions
#include <error.h> void error(int status, int errnum, const char *format, ...); void error_at_line(int status, int errnum, const char *filename, unsigned int linenum, const char *format, ...); extern unsigned int error_message_count; extern int error_one_per_line; extern void (*error_print_progname) (void);
error() is a general error-reporting function. It flushes
stdout, and then outputs to
stderr the program name, a colon and a space, the message specified by the printf(3)-style format string
format, and, if
errnum is nonzero, a second colon and a space followed by the string given by
strerror(errnum). Any arguments required for
format should follow
format in the argument list. The output is terminated by a newline character.
The program name printed by error() is the value of the global variable program_invocation_name(3).
program_invocation_name initially has the same value as
argv. The value of this variable can be modified to change the output of error().
The error_at_line() function is exactly the same as error(), except for the addition of the arguments
linenum. The output produced is as for error(), except that after the program name are written: a colon, the value of
filename, a colon, and the value of
linenum. The preprocessor values __LINE__ and __FILE__ may be useful when calling error_at_line(), but other values can also be used. For example, these arguments could refer to a location in an input file.
If the global variable
error_one_per_line is set nonzero, a sequence of error_at_line() calls with the same value of
linenum will result in only one message (the first) being output.
If the global variable
error_print_progname is assigned the address of a function (i.e., is not NULL), then that function is called instead of prefixing the message with the program name and colon. The function should print a suitable string to
For an explanation of the terms used in this section, see attributes(7).
|error()||Thread safety||MT-Safe locale|
|error_at_line()||Thread safety||MT-Unsafe race: error_at_line/error_one_per_line locale|
error_one_per_line variable is accessed (without any form of synchronization, but since it's an
int used once, it should be safe enough) and, if
error_one_per_line is set nonzero, the internal static variables (not exposed to users) used to hold the last printed filename and line number are accessed and modified without synchronization; the update is not atomic and it occurs before disabling cancellation, so it can be interrupted only after one of the two variables is modified. After that, error_at_line() is very much like error().
These functions and variables are GNU extensions, and should not be used in programs intended to be portable.
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