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PATCH: second go at `always' blocks
- X-seq: zsh-workers 20076
- From: Peter Stephenson <pws@xxxxxxx>
- To: Zsh hackers list <zsh-workers@xxxxxxxxxx>
- Subject: PATCH: second go at `always' blocks
- Date: Fri, 18 Jun 2004 12:05:31 +0100
- In-reply-to: "Bart Schaefer"'s message of "Wed, 16 Jun 2004 10:21:57 PDT." <Pine.LNX.4.44.0406161014150.7130-100000@xxxxxxxxxxxxxxxxxx>
- Mailing-list: contact zsh-workers-help@xxxxxxxxxx; run by ezmlm
Here is a second attempt following Oliver's and Bart's suggestions.
The new syntax is:
{
# execute normally
} always {
# execute always
# optionally reset error
(( TRY_BLOCK_ERROR = 0 ))
}
This doesn't clash with any currently valid zsh syntax, except that
we don't have parameter namespaces so can't say .sh.try_block_error.
Please read the description in grammar.yo (zshmisc.1) and see if
I've made it clear.
There is no special syntax for aborting the `try' block (I've continued
to use that language for clarity even though there is no corresponding
keyword).
Index: Doc/Zsh/grammar.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/grammar.yo,v
retrieving revision 1.8
diff -u -r1.8 grammar.yo
--- Doc/Zsh/grammar.yo 24 Jul 2001 13:16:09 -0000 1.8
+++ Doc/Zsh/grammar.yo 18 Jun 2004 10:56:08 -0000
@@ -234,6 +234,63 @@
item(tt({) var(list) tt(}))(
Execute var(list).
)
+findex(always)
+cindex(always blocks)
+cindex(try blocks)
+item(tt({) var(try-list) tt(} always {) var(always-list) tt(}))(
+First execute var(try-list). Regardless of errors, or tt(break),
+tt(continue), or tt(return) commands encountered within var(try-list),
+execute var(always-list). Execution then continues from the
+result of the execution of var(try-list); in other words, any error,
+or tt(break), tt(continue), or tt(return) command is treated in the
+normal way, as if var(always-list) were not present. The two
+chunks of code are referred to as the `try block' and the `always block'.
+
+Optional newlines or semicolons may appear after the tt(always);
+note, however, that they may em(not) appear between the preceeding
+closing brace and the tt(always).
+
+An `error' in this context is a condition such as a syntax error which
+causes the shell to abort execution of the current function, script, or
+list. Syntax errors encountered while the shell is parsing the
+code do not cause the var(always-list) to be executed. For example,
+an erroneously constructed tt(if) block in tt(try-list) would cause the
+shell to abort during parsing, so that tt(always-list) would not be
+executed, while an erroneous substitution such as tt(${*foo*}) would
+cause a run-time error, after which tt(always-list) would be executed.
+
+An error condition can be tested and reset with the special integer
+variable tt(TRY_BLOCK_ERROR). Outside an tt(always-list) the value is
+irrelevant, but it is initialised to tt(-1). Inside tt(always-list), the
+value is 1 if an error occurred in the tt(try-list), else 0. If
+tt(TRY_BLOCK_ERROR) is set to 0 during the tt(always-list), the error
+condition caused by the tt(try-list) is reset, and shell execution
+continues normally after the end of tt(always-list). Altering the value
+during the tt(try-list) is not useful (unless this forms part of an
+enclosing tt(always) block). Regardless of tt(TRY_BLOCK_ERROR), the
+normal shell status after the end of tt(always-list) is the value
+returned from tt(always-list).
+
+The following executes the given code, ignoring any errors it causes.
+This is an alternative to the usual convention of protecting code by
+executing it in a subshell.
+
+example({
+ # code which may cause an error
+ } always {
+ # This code is executed regardless of the error.
+ (( TRY_BLOCK_ERROR = 0 ))
+}
+# The error condition has been reset.)
+
+Note that the return status tt($?) after the end of the tt(always) block
+reflects the return status at the end of the var(try-list), consistent
+with other parts of the shell status.
+
+An tt(exit) command encountered in tt(try-list) does em(not) cause the
+execution of var(always-list). Instead, the shell exits immediately
+after any tt(EXIT) trap has been executed.
+)
findex(function)
xitem(tt(function) var(word) ... [ tt(()) ] [ var(term) ] tt({) var(list) tt(}))
xitem(var(word) ... tt(()) [ var(term) ] tt({) var(list) tt(}))
Index: Doc/Zsh/params.yo
===================================================================
RCS file: /cvsroot/zsh/zsh/Doc/Zsh/params.yo,v
retrieving revision 1.21
diff -u -r1.21 params.yo
--- Doc/Zsh/params.yo 6 Apr 2004 13:01:09 -0000 1.21
+++ Doc/Zsh/params.yo 18 Jun 2004 10:56:09 -0000
@@ -619,6 +619,14 @@
item(tt(signals))(
An array containing the names of the signals.
)
+vindex(TRY_BLOCK_ERROR)
+item(tt(TRY_BLOCK_ERROR) <S>)(
+In an tt(always) block, indicates whether the preceding list of code
+caused an error. The value is 1 to indicate an error, 0 otherwise.
+It may be reset, clearing the error condition. See
+ifzman(em(Complex Commands) in zmanref(zshmisc))\
+ifnzman(noderef(Complex Commands))
+)
vindex(TTY)
item(tt(TTY))(
The name of the tty associated with the shell, if any.
Index: Functions/MIME/zsh-mime-setup
===================================================================
RCS file: /cvsroot/zsh/zsh/Functions/MIME/zsh-mime-setup,v
retrieving revision 1.1
diff -u -r1.1 zsh-mime-setup
--- Functions/MIME/zsh-mime-setup 14 Sep 2003 19:37:35 -0000 1.1
+++ Functions/MIME/zsh-mime-setup 18 Jun 2004 10:56:09 -0000
@@ -62,9 +62,8 @@
zstyle -a :mime: mailcap cap_files ||
cap_files=(~/.mailcap /etc/mailcap)
-TRAPEXIT() { unfunction mime-setup-add-type >&/dev/null; return 0; }
-
-mime-setup-add-type() {
+{
+ mime-setup-add-type() {
local type suffix
local -a array
@@ -90,115 +89,117 @@
fi
fi
done
-}
+ }
-# Loop through files to find suffixes for MIME types.
-# Earlier entries take precedence, so the files need to be listed
-# with the user's own first. This also means pre-existing
-# values in suffix_type_map are respected.
-for file in $type_files; do
+ # Loop through files to find suffixes for MIME types.
+ # Earlier entries take precedence, so the files need to be listed
+ # with the user's own first. This also means pre-existing
+ # values in suffix_type_map are respected.
+ for file in $type_files; do
[[ -r $file ]] || continue
# For once we rely on the fact that read handles continuation
# lines ending in backslashes, i.e. there's no -r.
while read line; do
- # Skip blank or comment lines.
- [[ $line = [[:space:]]#(\#*|) ]] && continue
-
- # There are two types of line you find in MIME type files.
- # The original simple sort contains the type name then suffixes
- # separated by whitespace. However, Netscape insists
- # on adding lines with backslash continuation with
- # key="value" pairs. So we'd better handle both.
- if [[ $line = *=* ]]; then
- # Gory.
- # This relies on the fact that a typical entry:
- # type=video/x-mpeg2 desc="MPEG2 Video" exts="mpv2,mp2v"
- # looks like a parameter assignment. However, we really
- # don't want to be screwed up by future extensions,
- # so we split the elements to an array and pick out the
- # ones we're interested in.
- type= exts=
-
- # Syntactically split line to preserve quoted words.
- array=(${(z)line})
- for elt in $array; do
- if [[ $elt = (type|exts)=* ]]; then
- eval $elt
- fi
- done
+ # Skip blank or comment lines.
+ [[ $line = [[:space:]]#(\#*|) ]] && continue
- # Get extensions by splitting on comma
- array=(${(s.,.)exts})
-
- [[ -n $type ]] && mime-setup-add-type $type $array
- else
- # Simple.
- mime-setup-add-type ${=line}
- fi
+ # There are two types of line you find in MIME type files.
+ # The original simple sort contains the type name then suffixes
+ # separated by whitespace. However, Netscape insists
+ # on adding lines with backslash continuation with
+ # key="value" pairs. So we'd better handle both.
+ if [[ $line = *=* ]]; then
+ # Gory.
+ # This relies on the fact that a typical entry:
+ # type=video/x-mpeg2 desc="MPEG2 Video" exts="mpv2,mp2v"
+ # looks like a parameter assignment. However, we really
+ # don't want to be screwed up by future extensions,
+ # so we split the elements to an array and pick out the
+ # ones we're interested in.
+ type= exts=
+
+ # Syntactically split line to preserve quoted words.
+ array=(${(z)line})
+ for elt in $array; do
+ if [[ $elt = (type|exts)=* ]]; then
+ eval $elt
+ fi
+ done
+
+ # Get extensions by splitting on comma
+ array=(${(s.,.)exts})
+
+ [[ -n $type ]] && mime-setup-add-type $type $array
+ else
+ # Simple.
+ mime-setup-add-type ${=line}
+ fi
done <$file
-done
-
+ done
+} always {
+ unfunction mime-setup-add-type >&/dev/null
+}
# Loop through files to find handlers for types.
for file in $cap_files; do
- [[ -r $file ]] || continue
+ [[ -r $file ]] || continue
- # Oh, great. We need to preserve backslashes inside the line,
- # but need to manage continuation lines.
- while read -r line; do
- # Skip blank or comment lines.
- [[ $line = [[:space:]]#(\#*|) ]] && continue
-
- while [[ $line = (#b)(*)\\ ]]; do
- line=$match[1]
- read -r line2 || break
- line+=$line2
- done
-
- # Guess what, this file has a completely different format.
- # See mailcap(4).
- # The biggest unpleasantness here is that the fields are
- # delimited by semicolons, but the command field, which
- # is the one we want to extract, may itself contain backslashed
- # semicolons.
- if [[ $line = (#b)[[:space:]]#([^[:space:]\;]##)[[:space:]]#\;(*) ]]
- then
- # this is the only form we can handle, but there's no point
- # issuing a warning for other forms.
- type=$match[1]
- line=$match[2]
- # See if it has flags after the command.
- if [[ $line = (#b)(([^\;\\]|\\\;|\\[^\;])#)\;(*) ]]; then
- line=$match[1]
- flags=$match[3]
- else
- flags=
- fi
- # Remove quotes from semicolons
- line=${line//\\\;/\;}
- # and remove any surrounding white space --- this might
- # make the handler empty.
- line=${${line##[[:space:]]#}%%[[:space:]]}
- if [[ -z $type_handler_map[$type] ]]; then
- if [[ -n $o_verbose ]]; then
- print -r "Adding handler for type $type:
+ # Oh, great. We need to preserve backslashes inside the line,
+ # but need to manage continuation lines.
+ while read -r line; do
+ # Skip blank or comment lines.
+ [[ $line = [[:space:]]#(\#*|) ]] && continue
+
+ while [[ $line = (#b)(*)\\ ]]; do
+ line=$match[1]
+ read -r line2 || break
+ line+=$line2
+ done
+
+ # Guess what, this file has a completely different format.
+ # See mailcap(4).
+ # The biggest unpleasantness here is that the fields are
+ # delimited by semicolons, but the command field, which
+ # is the one we want to extract, may itself contain backslashed
+ # semicolons.
+ if [[ $line = (#b)[[:space:]]#([^[:space:]\;]##)[[:space:]]#\;(*) ]]
+ then
+ # this is the only form we can handle, but there's no point
+ # issuing a warning for other forms.
+ type=$match[1]
+ line=$match[2]
+ # See if it has flags after the command.
+ if [[ $line = (#b)(([^\;\\]|\\\;|\\[^\;])#)\;(*) ]]; then
+ line=$match[1]
+ flags=$match[3]
+ else
+ flags=
+ fi
+ # Remove quotes from semicolons
+ line=${line//\\\;/\;}
+ # and remove any surrounding white space --- this might
+ # make the handler empty.
+ line=${${line##[[:space:]]#}%%[[:space:]]}
+ if [[ -z $type_handler_map[$type] ]]; then
+ if [[ -n $o_verbose ]]; then
+ print -r "Adding handler for type $type:
$line" >&2
- fi
- type_handler_map[$type]=$line
- type_flags_map[$type]=$flags
- if [[ -n $flags && -n $o_verbose ]]; then
- print -r " with flags $flags" >&2
- fi
- elif [[ -n $o_verbose ]]; then
- print -r "Skipping handler for already defined type $type:
+ fi
+ type_handler_map[$type]=$line
+ type_flags_map[$type]=$flags
+ if [[ -n $flags && -n $o_verbose ]]; then
+ print -r " with flags $flags" >&2
+ fi
+ elif [[ -n $o_verbose ]]; then
+ print -r "Skipping handler for already defined type $type:
$line" >&2
- if [[ -n $flags ]]; then
- print -r " with flags $flags" >&2
- fi
- fi
+ if [[ -n $flags ]]; then
+ print -r " with flags $flags" >&2
fi
- done <$file
+ fi
+ fi
+ done <$file
done
Index: Src/exec.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/exec.c,v
retrieving revision 1.64
diff -u -r1.64 exec.c
--- Src/exec.c 2 Jun 2004 22:14:25 -0000 1.64
+++ Src/exec.c 18 Jun 2004 10:56:16 -0000
@@ -137,10 +137,10 @@
/* Execution functions. */
-static int (*execfuncs[]) _((Estate, int)) = {
+static int (*execfuncs[WC_COUNT-WC_CURSH]) _((Estate, int)) = {
execcursh, exectime, execfuncdef, execfor, execselect,
execwhile, execrepeat, execcase, execif, execcond,
- execarith, execautofn
+ execarith, execautofn, exectry
};
/* structure for command builtin for when it is used with -v or -V */
@@ -325,6 +325,9 @@
{
Wordcode end = state->pc + WC_CURSH_SKIP(state->pc[-1]);
+ /* Skip word only used for try/always */
+ state->pc++;
+
if (!list_pipe && thisjob != list_pipe_job && !hasprocs(thisjob))
deletejob(jobtab + thisjob);
cmdpush(CS_CURSH);
@@ -2475,6 +2478,9 @@
subsh_close = -1;
/* If we're forked (and we should be), no need to return */
DPUTS(last1 != 1 && !forked, "BUG: not exiting?");
+ DPUTS(type != WC_SUBSH, "Not sure what we're doing.");
+ /* Skip word only used for try/always blocks */
+ state->pc++;
execlist(state, 0, 1);
}
}
Index: Src/loop.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/loop.c,v
retrieving revision 1.13
diff -u -r1.13 loop.c
--- Src/loop.c 2 Jun 2004 22:14:26 -0000 1.13
+++ Src/loop.c 18 Jun 2004 10:56:17 -0000
@@ -616,3 +616,68 @@
return lastval;
}
+
+/*
+ * Errflag from `try' block, may be reset in `always' block.
+ * Accessible from an integer parameter, so needs to be a zlong.
+ */
+
+/**/
+zlong
+try_errflag = -1;
+
+/**/
+int
+exectry(Estate state, int do_exec)
+{
+ Wordcode end, always;
+ int endval;
+ int save_retflag, save_breaks, save_loops, save_contflag;
+ zlong save_try_errflag;
+
+ end = state->pc + WC_TRY_SKIP(state->pc[-1]);
+ always = state->pc + 1 + WC_TRY_SKIP(*state->pc);
+ state->pc++;
+ pushheap();
+ cmdpush(CS_CURSH);
+
+ /* The :try clause */
+ execlist(state, 1, do_exec);
+
+ /* Don't record errflag here, may be reset. */
+ endval = lastval;
+
+ freeheap();
+
+ cmdpop();
+ cmdpush(CS_ALWAYS);
+
+ /* The always clause. */
+ save_try_errflag = try_errflag;
+ try_errflag = (zlong)errflag;
+ errflag = 0;
+ save_retflag = retflag;
+ retflag = 0;
+ save_breaks = breaks;
+ breaks = 0;
+ save_loops = loops;
+ loops = 0;
+ save_contflag = contflag;
+ contflag = 0;
+
+ state->pc = always;
+ execlist(state, 1, do_exec);
+
+ errflag = try_errflag ? 1 : 0;
+ try_errflag = save_try_errflag;
+ retflag = save_retflag;
+ breaks = save_breaks;
+ loops = save_loops;
+ contflag = save_contflag;
+
+ cmdpop();
+ popheap();
+ state->pc = end;
+
+ return endval;
+}
Index: Src/params.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/params.c,v
retrieving revision 1.85
diff -u -r1.85 params.c
--- Src/params.c 2 Jun 2004 22:14:26 -0000 1.85
+++ Src/params.c 18 Jun 2004 10:56:19 -0000
@@ -106,6 +106,7 @@
/* 0 if this $TERM setup is usable, otherwise it contains TERM_* flags */
+
/**/
mod_export int termflags;
@@ -191,6 +192,7 @@
IPDEF5("LINES", &lines, zlevarsetfn),
IPDEF5("OPTIND", &zoptind, intvarsetfn),
IPDEF5("SHLVL", &shlvl, intvarsetfn),
+IPDEF5("TRY_BLOCK_ERROR", &try_errflag, intvarsetfn),
#define IPDEF7(A,B) {NULL,A,PM_SCALAR|PM_SPECIAL,BR((void *)B),SFN(strvarsetfn),GFN(strvargetfn),stdunsetfn,0,NULL,NULL,NULL,0}
IPDEF7("OPTARG", &zoptarg),
Index: Src/parse.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/parse.c,v
retrieving revision 1.44
diff -u -r1.44 parse.c
--- Src/parse.c 2 Jun 2004 22:14:26 -0000 1.44
+++ Src/parse.c 18 Jun 2004 10:56:20 -0000
@@ -1330,25 +1330,55 @@
}
/*
- * subsh : ( INPAR | INBRACE ) list ( OUTPAR | OUTBRACE )
+ * subsh : INPAR list OUTPAR |
+ * INBRACE list OUTBRACE [ "always" INBRACE list OUTBRACE ]
*/
/**/
static void
par_subsh(int *complex)
{
- int oecused = ecused, otok = tok, p;
+ int oecused = ecused, otok = tok, p, pp;
p = ecadd(0);
+ /* Extra word only needed for always block */
+ pp = ecadd(0);
yylex();
par_list(complex);
ecadd(WCB_END());
if (tok != ((otok == INPAR) ? OUTPAR : OUTBRACE))
YYERRORV(oecused);
- ecbuf[p] = (otok == INPAR ? WCB_SUBSH(ecused - 1 - p) :
- WCB_CURSH(ecused - 1 - p));
incmdpos = 1;
yylex();
+
+ /* Optional always block. No intervening SEPERs allowed. */
+ if (otok == INBRACE && tok == STRING && !strcmp(tokstr, "always")) {
+ ecbuf[pp] = WCB_TRY(ecused - 1 - pp);
+ incmdpos = 1;
+ do {
+ yylex();
+ } while (tok == SEPER);
+
+ if (tok != INBRACE)
+ YYERRORV(oecused);
+ cmdpop();
+ cmdpush(CS_ALWAYS);
+
+ yylex();
+ par_save_list(complex);
+ while (tok == SEPER)
+ yylex();
+
+ incmdpos = 1;
+
+ if (tok != OUTBRACE)
+ YYERRORV(oecused);
+ yylex();
+ ecbuf[p] = WCB_TRY(ecused - 1 - p);
+ } else {
+ ecbuf[p] = (otok == INPAR ? WCB_SUBSH(ecused - 1 - p) :
+ WCB_CURSH(ecused - 1 - p));
+ }
}
/*
Index: Src/prompt.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/prompt.c,v
retrieving revision 1.18
diff -u -r1.18 prompt.c
--- Src/prompt.c 28 May 2004 19:21:46 -0000 1.18
+++ Src/prompt.c 18 Jun 2004 10:56:21 -0000
@@ -49,7 +49,7 @@
/* parser states, for %_ */
-static char *cmdnames[] = {
+static char *cmdnames[CS_COUNT] = {
"for", "while", "repeat", "select",
"until", "if", "then", "else",
"elif", "math", "cond", "cmdor",
@@ -57,7 +57,7 @@
"case", "function", "subsh", "cursh",
"array", "quote", "dquote", "bquote",
"cmdsubst", "mathsubst", "elif-then", "heredoc",
- "heredocd", "brace", "braceparam",
+ "heredocd", "brace", "braceparam", "always",
};
/* The buffer into which an expanded and metafied prompt is being written, *
Index: Src/text.c
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/text.c,v
retrieving revision 1.13
diff -u -r1.13 text.c
--- Src/text.c 4 Feb 2003 11:23:05 -0000 1.13
+++ Src/text.c 18 Jun 2004 10:56:21 -0000
@@ -350,6 +350,8 @@
taddnl();
n = tpush(code, 1);
n->u._subsh.end = state->pc + WC_SUBSH_SKIP(code);
+ /* skip word only use for try/always */
+ state->pc++;
} else {
state->pc = s->u._subsh.end;
tindent--;
@@ -365,6 +367,8 @@
taddnl();
n = tpush(code, 1);
n->u._subsh.end = state->pc + WC_CURSH_SKIP(code);
+ /* skip word only use for try/always */
+ state->pc++;
} else {
state->pc = s->u._subsh.end;
tindent--;
@@ -721,6 +725,30 @@
taddstr("))");
stack = 1;
break;
+ case WC_TRY:
+ if (!s) {
+ taddstr("{");
+ tindent++;
+ taddnl();
+ n = tpush(code, 0);
+ state->pc++;
+ /* this is the end of the try block alone */
+ n->u._subsh.end = state->pc + WC_CURSH_SKIP(state->pc[-1]);
+ } else if (!s->pop) {
+ state->pc = s->u._subsh.end;
+ tindent--;
+ taddnl();
+ taddstr("} always {");
+ tindent++;
+ taddnl();
+ s->pop = 1;
+ } else {
+ tindent--;
+ taddnl();
+ taddstr("}");
+ stack = 1;
+ }
+ break;
case WC_END:
stack = 1;
break;
Index: Src/zsh.h
===================================================================
RCS file: /cvsroot/zsh/zsh/Src/zsh.h,v
retrieving revision 1.56
diff -u -r1.56 zsh.h
--- Src/zsh.h 20 Apr 2004 12:11:16 -0000 1.56
+++ Src/zsh.h 18 Jun 2004 10:56:22 -0000
@@ -580,6 +580,10 @@
#define WC_COND 17
#define WC_ARITH 18
#define WC_AUTOFN 19
+#define WC_TRY 20
+
+/* increment as necessary */
+#define WC_COUNT 21
#define WCB_END() wc_bld(WC_END, 0)
@@ -657,6 +661,9 @@
#define WC_REPEAT_SKIP(C) wc_data(C)
#define WCB_REPEAT(O) wc_bld(WC_REPEAT, (O))
+#define WC_TRY_SKIP(C) wc_data(C)
+#define WCB_TRY(O) wc_bld(WC_TRY, (O))
+
#define WC_CASE_TYPE(C) (wc_data(C) & 3)
#define WC_CASE_HEAD 0
#define WC_CASE_OR 1
@@ -1695,6 +1702,10 @@
#define CS_HEREDOCD 28
#define CS_BRACE 29
#define CS_BRACEPAR 30
+#define CS_ALWAYS 31
+
+/* Increment as necessary */
+#define CS_COUNT 32
/*********************
* Memory management *
--
Peter Stephenson <pws@xxxxxxx> Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK Tel: +44 (0)1223 692070
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