From @arc

via RT <perlbug-followup@perl.org> wrote:

The perlfunc doc (aka http://perldoc.perl.org/functions/sprintf.html)
has this example:

printf '<%*2$s>', "a", 6; # prints "< a>"

Running it with perl -w, in perl 5.22.0, produces a warning:

Redundant argument in printf at try.pl line 1.

Maybe I'm missing something obvious, but it sure seems like both
arguments are being used; the a is the value and the 6 is the field
width. So the warning seems incorrect. Help?

Thanks for the report. I agree that it's incorrect for Perl to emit
this warning.

This patch against blead is currently smoking as smoke-me/arc/rt125469:

From: Aaron Crane <arc@cpan.org>
Date: Mon, 29 Jun 2015 16:35:11 +0100
Subject: [PATCH] sv_vcatpvfn_flags(): make warnings more precise

- RT#125469 points out that no "redundant argument" warning should be emitted
for code like C<< printf '<%*2$s>', "a", 6 >>; that's now fixed.

- We no longer emit a "missing argument" warning for invalid format strings,
so C<< printf '%4$K %d', 17 >> now emits one "invalid" warning, and no
other warnings. (Perl 5.12 and subsequent versions have inappropriately
emitted a "missing argument" warning in this case.)

- We no longer treat the invalid format string in C<< printf '%1$$d', 17 >>
as containing an explicit index, so (a) we emit an "invalid" warning for
the double "$", and (b) we emit a "redundant argument" warning for the
trailing argument. The "redundant argument" warning is new in this
situation.

sv.c | 65 ++++++++++++++++++++++++++++++++++++----------------------
t/op/sprintf.t | 9 ++++----
2 files changed, 46 insertions(+), 28 deletions(-)

Inline Patch

diff --git a/sv.c b/sv.c
index b4a36e5..d3debba 100644
--- a/sv.c
+++ b/sv.c
@@ -10594,16 +10594,16 @@ Perl_sv_vsetpvfn(pTHX_ SV *const sv, const

char *const pat, const STRLEN patlen,

/*
- * Warn of missing argument to sprintf, and then return a defined value
- * to avoid inappropriate "use of uninit" warnings [perl #71000].
+ * Warn of missing argument to sprintf. The value used in place of such
+ * arguments should be &PL_sv_no; an undefined value would yield
+ * inappropriate "use of uninit" warnings [perl #71000].
*/
-STATIC SV*
-S_vcatpvfn_missing_argument(pTHX) {
+STATIC void
+S_warn_vcatpvfn_missing_argument(pTHX) {
if (ckWARN(WARN_MISSING)) {
Perl_warner(aTHX_ packWARN(WARN_MISSING), "Missing argument in %s",
PL_op ? OP_DESC(PL_op) : "sv_vcatpvfn()");
}
- return &PL_sv_no;
}

@@ -11032,6 +11032,17 @@ S_hextract(pTHX_ const NV nv, int* exponent,
U8* vhex, U8* vend)
return v;
}

+/* Helper for sv_vcatpvfn_flags(). */
+#define FETCH_VCATPVFN_ARGUMENT(var, in_range, expr) \
+ STMT_START { \
+ if (in_range) \
+ (var) = (expr); \
+ else { \
+ (var) = &PL_sv_no; /* [perl #71000] */ \
+ arg_missing = TRUE; \
+ } \
+ } STMT_END
+
void
Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat,
const STRLEN patlen,
va_list *const args, SV **const svargs, const
I32 svmax, bool *const maybe_tainted,
@@ -11087,7 +11098,7 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
sv_catsv_nomg(sv, *svargs);
}
else
- S_vcatpvfn_missing_argument(aTHX);
+ S_warn_vcatpvfn_missing_argument(aTHX);
return;
}
if (args && patlen == 3 && pat[0] == '%' &&
@@ -11161,6 +11172,8 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
STRLEN precis = 0;
const I32 osvix = svix;
bool is_utf8 = FALSE; /* is this item utf8? */
+ bool used_explicit_ix = FALSE;
+ bool arg_missing = FALSE;
#ifdef HAS_LDBL_SPRINTF_BUG
/* This is to try to fix a bug with irix/nonstop-ux/powerux and
with sfio - Allen <allens@cpan.org> */
@@ -11326,11 +11339,7 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
if (*q == '$') {
++q;
efix = width;
- if (!no_redundant_warning)
- /* I've forgotten if it's a better
- micro-optimization to always set this or to
- only set it if it's unset */
- no_redundant_warning = TRUE;
+ used_explicit_ix = TRUE;
} else {
goto gotwidth;
}
@@ -11371,9 +11380,12 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
tryasterisk:
if (*q == '*') {
q++;
- if ( (ewix = expect_number(&q)) )
- if (*q++ != '$')
+ if ( (ewix = expect_number(&q)) ) {
+ if (*q++ == '$')
+ used_explicit_ix = TRUE;
+ else
goto unknown;
+ }
asterisk = TRUE;
}
if (*q == 'v') {
@@ -11401,11 +11413,11 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
if (args)
vecsv = va_arg(*args, SV*);
else if (evix) {
- vecsv = (evix > 0 && evix <= svmax)
- ? svargs[evix-1] : S_vcatpvfn_missing_argument(aTHX);
+ FETCH_VCATPVFN_ARGUMENT(
+ vecsv, evix > 0 && evix <= svmax, svargs[evix-1]);
} else {
- vecsv = svix < svmax
- ? svargs[svix++] : S_vcatpvfn_missing_argument(aTHX);
+ FETCH_VCATPVFN_ARGUMENT(
+ vecsv, svix < svmax, svargs[svix++]);
}
dotstr = SvPV_const(vecsv, dotstrlen);
/* Keep the DO_UTF8 test *after* the SvPV call, else things go
@@ -11573,11 +11585,10 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
if (!vectorize && !args) {
if (efix) {
const I32 i = efix-1;
- argsv = (i >= 0 && i < svmax)
- ? svargs[i] : S_vcatpvfn_missing_argument(aTHX);
+ FETCH_VCATPVFN_ARGUMENT(argsv, i >= 0 && i < svmax, svargs[i]);
} else {
- argsv = (svix >= 0 && svix < svmax)
- ? svargs[svix++] : S_vcatpvfn_missing_argument(aTHX);
+ FETCH_VCATPVFN_ARGUMENT(argsv, svix >= 0 && svix < svmax,
+ svargs[svix++]);
}
}

@@ -11680,7 +11691,7 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
if (vectorize) {
STRLEN ulen;
if (!veclen)
- continue;
+ goto donevalidconversion;
if (vec_utf8)
uv = utf8n_to_uvchr(vecstr, veclen, &ulen,
UTF8_ALLOW_ANYUV);
@@ -11785,7 +11796,7 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
STRLEN ulen;
vector:
if (!veclen)
- continue;
+ goto donevalidconversion;
if (vec_utf8)
uv = utf8n_to_uvchr(vecstr, veclen, &ulen,
UTF8_ALLOW_ANYUV);
@@ -12447,7 +12458,7 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
}
else
sv_setuv_mg(argsv, has_utf8 ? (UV)sv_len_utf8(sv) : (UV)i);
- continue; /* not "break" */
+ goto donevalidconversion;

/* UNKNOWN */

@@ -12572,6 +12583,12 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,
const char *const pat, const STRLEN p
esignlen = 0;
goto vector;
}
+
+ donevalidconversion:
+ if (used_explicit_ix)
+ no_redundant_warning = TRUE;
+ if (arg_missing)
+ S_warn_vcatpvfn_missing_argument(aTHX);
}

/* Now that we've consumed all our printf format arguments (svix)

Inline Patch

diff --git a/t/op/sprintf.t b/t/op/sprintf.t
index c927a94..e11287c 100644
--- a/t/op/sprintf.t
+++ b/t/op/sprintf.t
@@ -647,7 +647,8 @@ __END__
 >%y<        >''<          >%y INVALID REDUNDANT<
 >%z<        >''<          >%z INVALID REDUNDANT<
 >%2$d %1$d< >[12, 34]< >34 12<
->%*2$d< >[12, 3]< > 12 REDUNDANT<
+>%*2$d< >[12, 3]< > 12<             >RT#125469<
+>%*3$d< >[12, 9, 3]< > 12<             >related to RT#125469<
 >%2$d %d< >[12, 34]< >34 12<
 >%2$d %d %d< >[12, 34]< >34 12 34<
 >%3$d %d %d< >[12, 34, 56]< >56 12 34<
@@ -655,8 +656,8 @@ __END__
 >%*3$2$d %d< >[12, 34, 3]< >%*3$2$d 12 INVALID REDUNDANT<
 >%2$d< >12< >0 MISSING<
 >%0$d< >12< >%0$d INVALID REDUNDANT<
->%1$$d< >12< >%1$$d INVALID<
->%1$1$d< >12< >%1$1$d INVALID<
+>%1$$d< >12< >%1$$d INVALID REDUNDANT<
+>%1$1$d< >12< >%1$1$d INVALID REDUNDANT<
 >%*2$*2$d< >[12, 3]< >%*2$*2$d INVALID REDUNDANT<
 >%*2*2$d< >[12, 3]< >%*2*2$d INVALID REDUNDANT<
 >%*2$1d< >[12, 3]< >%*2$1d INVALID REDUNDANT<
@@ -713,7 +714,7 @@ __END__
 >%V-%s< >["Hello"]< >%V-Hello INVALID<
 >%K %d %d< >[13, 29]< >%K 13 29 INVALID<
 >%*.*K %d< >[13, 29, 76]< >%*.*K 13 INVALID REDUNDANT<
->%4$K %d< >[45, 67]< >%4$K 45 MISSING INVALID<
+>%4$K %d< >[45, 67]< >%4$K 45 INVALID REDUNDANT<
 >%d %K %d< >[23, 45]< >23 %K 45 INVALID<
 >%*v*999\$d %d %d< >[11, 22, 33]< >%*v*999\$d 11 22 INVALID REDUNDANT<
 >%#b< >0< >0<

I also believe that this bug is a regression that warrants a fix in maint\, hopefully to be released as part of 5\.22\.1\. However\, my blead patch is unsuitable for that purpose\, as it will also yield additional warnings for some other code\. $It ensures that an invalid format specification is never treated as containing an explicit argument index\, so code like C\<\< printf '%1$$d'\, 17 >> will get a "redundant" warning for the 17\, as well as an "invalid" warning for the malformed '%1$$d'\.$ So I'm also smoking this simpler patch as smoke\-me/arc/rt125469\-maint\, in the expectation that it could be applied to maint:

From: Aaron Crane <arc@cpan.org>
Date: Mon, 29 Jun 2015 16:55:14 +0100
Subject: [PATCH] sv_vcatpvfn_flags(): no "redundant arg" warnings for '%*2$d'

This addresses RT#125469: if the format string uses an explicit index for a
field width, that should suppress any "redundant argument" warnings, in
just the same way as an explicit index does when used to specify a format
argument.

Blead has a more careful reworking of the way printf warnings work, but that
change is unsuitable for maint, as it can lead to additional warnings being
emitted for some invalid format strings. This smaller change ensures that
maint (5.22.1-to-be) always emits strictly fewer warnings than 5.22.0.

sv.c | 7 +++++--
t/op/sprintf.t | 9 +++++----
2 files changed, 10 insertions(+), 6 deletions(-)

Inline Patch

diff --git a/sv.c b/sv.c
index 8440763..6afc5a6 100644
--- a/sv.c
+++ b/sv.c
@@ -11522,9 +11522,12 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv,

const char *const pat, const STRLEN p tryasterisk: if $\*q == '\*'$ \{ q\+\+; \- if $ \(ewix = expect\_number\(&q$\) \) \- if $\*q\+\+ \!= '$'$ \+ if $ \(ewix = expect\_number\(&q$\) \) \{ \+ if $\*q\+\+ == '$'$ \+ no\_redundant\_warning = TRUE; \+ else goto unknown; \+ \} asterisk = TRUE; \} if $\*q == 'v'$ \{

Inline Patch

diff --git a/t/op/sprintf.t b/t/op/sprintf.t
index 967b5d3..e6ef617 100644
--- a/t/op/sprintf.t
+++ b/t/op/sprintf.t
@@ -647,19 +647,20 @@ __END__
 >%y<        >''<          >%y INVALID REDUNDANT<
 >%z<        >''<          >%z INVALID REDUNDANT<
 >%2$d %1$d< >[12, 34]< >34 12<
->%*2$d< >[12, 3]< > 12 REDUNDANT<
+>%*2$d< >[12, 3]< > 12<             >RT#125469<
+>%*3$d< >[12, 9, 3]< > 12<             >related to RT#125469<
 >%2$d %d< >[12, 34]< >34 12<
 >%2$d %d %d< >[12, 34]< >34 12 34<
 >%3$d %d %d< >[12, 34, 56]< >56 12 34<
 >%2$*3$d %d< >[12, 34, 3]< > 34 12<
->%*3$2$d %d< >[12, 34, 3]< >%*3$2$d 12 INVALID REDUNDANT<
+>%*3$2$d %d< >[12, 34, 3]< >%*3$2$d 12 INVALID<
 >%2$d< >12< >0 MISSING<
 >%0$d< >12< >%0$d INVALID REDUNDANT<
 >%1$$d< >12< >%1$$d INVALID<
 >%1$1$d< >12< >%1$1$d INVALID<
->%*2$*2$d< >[12, 3]< >%*2$*2$d INVALID REDUNDANT<
+>%*2$*2$d< >[12, 3]< >%*2$*2$d INVALID<
 >%*2*2$d< >[12, 3]< >%*2*2$d INVALID REDUNDANT<
->%*2$1d< >[12, 3]< >%*2$1d INVALID REDUNDANT<
+>%*2$1d< >[12, 3]< >%*2$1d INVALID<
 >%0v2.2d< >''< ><
 >%vc,%d< >[63, 64, 65]< >%vc,63 INVALID REDUNDANT<
 >%v%,%d< >[63, 64, 65]< >%v%,63 INVALID REDUNDANT<

--

Aaron Crane ** http://aaroncrane.co.uk/

"redundant argument in printf" warning and computed field widths #14772

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