# HG changeset patch
# User Francisco J Ballesteros <nemo.mbox@gmail.com>
# Date 1328893756 0
# Node ID 257203b800f6651da9c0a62c8d3bf2d50194f682
# Parent  34ea01195f9f3c474ccda369eefcf36aa2cc816f
error: handling like in the kernel for user programs.
ix is now using this for it's file server.

R=nixiedev, rminnich, john, nemo, quanstro
CC=nix-dev
http://codereview.appspot.com/5610052

diff -r 34ea01195f9f -r 257203b800f6 sys/include/error.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/include/error.h	Fri Feb 10 17:09:16 2012 +0000
@@ -0,0 +1,19 @@
+#pragma	lib	"liberror.a"
+#pragma src "/sys/src/liberror"
+
+typedef struct Error Error;
+
+struct Error {
+	int	nerr;
+	int	nlabel;
+	jmp_buf label[1];	/* of [stack] actually */
+};
+
+#pragma	varargck	argpos	error	1
+#pragma varargck		argpos	esmprint 1
+
+void	errinit(int stack);
+void	noerror(void);
+void	error(char* msg, ...);
+#define	catcherror()	setjmp((*__ep)->label[(*__ep)->nerr++])
+extern Error**	__ep;
diff -r 34ea01195f9f -r 257203b800f6 sys/man/2/error
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/man/2/error	Fri Feb 10 17:09:16 2012 +0000
@@ -0,0 +1,70 @@
+.TH ERROR 2
+.SH NAME
+errinit, noerror, error, catcherror \- local error handling utilities
+.SH SYNOPSIS
+.B #include <u.h>
+.br
+.B #include <libc.h>
+.br
+.B #include <error.h>
+.PP
+.B
+void	errinit(int stack)
+.br
+.B
+void	noerror(void)
+.br
+.B
+void	error(char* msg, ...)
+.br
+.B
+void	catcherror(void)
+.SH DESCRIPTION
+These routiles are tools for error handling.
+.IR catcherror ,
+.IR noerror ,
+.IR error ,
+and
+.IR errinit
+provide exeption handling for C, in the same style of the similar routines used in
+the kernel.
+They can be used both with and without
+the
+.IR thread (2)
+library.
+.PP
+.I Errinit
+should be called before using any other. It should be called by each thread/process
+using the error handling mechanism. Its argument,
+indicaties the desired depth of the error stack for the calling process.
+.PP
+.I Catcherror
+install an exception handling point.
+.I Noerror
+declares that there was no error catched, similar to the
+.I poperror
+function in the kernel.
+.I Error
+raises an error. If the argument is nil, the error string is unaltered. See the example.
+.SH SOURCE
+.B /sys/src/liberror
+.SH EXAMPLE
+Catch an error, and raise one.
+.PP
+.EX
+void f(void)
+{
+	error("catch this!");
+}
+
+void
+main(int argc, char **argv)
+{
+	errinit(32);
+	if (catcherror()){
+		sysfatal("catched: %r");
+	}
+	f();
+	noerror();
+}
+.EE
diff -r 34ea01195f9f -r 257203b800f6 sys/src/liberror/error.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/src/liberror/error.c	Fri Feb 10 17:09:16 2012 +0000
@@ -0,0 +1,46 @@
+#include <u.h>
+#include <libc.h>
+#include <error.h>
+
+Error**	__ep;
+
+void
+errinit(int stack)
+{
+	Error *e;
+
+	e = mallocz(sizeof(Error) + sizeof(e->label)*(stack-1), 1);
+	if(e == nil)
+		sysfatal("errinit: no memory");
+	if(__ep == nil)
+		__ep = privalloc();
+	*__ep = e;
+	e->nlabel = stack;
+}
+
+void
+noerror(void)
+{
+	if((*__ep)->nerr > (*__ep)->nlabel - 3)
+		sysfatal("error stack about to overflow");
+	if((*__ep)->nerr-- == 0)
+		sysfatal("noerror w/o catcherror");
+}
+
+void
+error(char* msg, ...)
+{
+	char	buf[500];
+	va_list	arg;
+
+	if(msg != nil){
+		va_start(arg, msg);
+		vseprint(buf, buf+sizeof(buf), msg, arg);
+		va_end(arg);
+		werrstr("%s", buf);
+	}
+	if((*__ep)->nerr == 0)
+		sysfatal("%s", buf);
+	(*__ep)->nerr--;
+	longjmp((*__ep)->label[(*__ep)->nerr], 1);
+}
diff -r 34ea01195f9f -r 257203b800f6 sys/src/liberror/mkfile
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/sys/src/liberror/mkfile	Fri Feb 10 17:09:16 2012 +0000
@@ -0,0 +1,15 @@
+</$objtype/mkfile
+
+LIB=/$objtype/lib/liberror.a
+OFILES=\
+	error.$O\
+
+HFILES=/sys/include/error.h
+
+UPDATE=\
+	mkfile\
+	$HFILES\
+	${OFILES:%.$O=%.c}\
+	${LIB:/$objtype/%=/386/%}\
+
+</sys/src/cmd/mksyslib