until( assignment ) doesn't warn when while (assignment ) does

[p5pRT]

Migrated from rt.perl.org#127333 (status was 'resolved')

Searchable as RT127333$

[p5pRT]

From @tonycoz

This is similar to #127122, but doesn't have quite as simple a fix.

  $ ./perl -Ilib -Mwarnings=syntax -le 'while ($x = 0) { }'
  Found = in conditional, should be == at -e line 1.
  $ ./perl -Ilib -Mwarnings=syntax -le 'until ($x = 1) { }'
  $

$ ./perl -Ilib -V
Summary of my perl5 (revision 5 version 23 subversion 8) configuration​:
  Derived from​: 08b3e84
  Platform​:
  osname=linux, osvers=3.16.0-4-amd64, archname=x86_64-linux
  uname='linux mars 3.16.0-4-amd64 #1 smp debian 3.16.7-ckt20-1+deb8u2 (2016-01-02) x86_64 gnulinux '
  config_args='-des -Dusedevel -Uversiononly -DDEBUGGING -Dprefix=/home/tony/perl/blead -Doptimize=-O0 -g3'
  hint=recommended, useposix=true, d_sigaction=define
  useithreads=undef, usemultiplicity=undef
  use64bitint=define, use64bitall=define, uselongdouble=undef
  usemymalloc=n, bincompat5005=undef
  Compiler​:
  cc='cc', ccflags ='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2',
  optimize='-O0 -g3',
  cppflags='-fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
  ccversion='', gccversion='4.9.2', gccosandvers=''
  intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678, doublekind=3
  d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=16, longdblkind=3
  ivtype='long', ivsize=8, nvtype='double', nvsize=8, Off_t='off_t', lseeksize=8
  alignbytes=8, prototype=define
  Linker and Libraries​:
  ld='cc', ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib
  libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
  perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a
  gnulibc_version='2.19'
  Dynamic Linking​:
  dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
  cccdlflags='-fPIC', lddlflags='-shared -O0 -g3 -L/usr/local/lib -fstack-protector-strong'

Characteristics of this binary (from libperl)​:
  Compile-time options​: DEBUGGING HAS_TIMES PERLIO_LAYERS PERL_COPY_ON_WRITE
  PERL_DONT_CREATE_GVSV
  PERL_HASH_FUNC_ONE_AT_A_TIME_HARD PERL_MALLOC_WRAP
  PERL_PRESERVE_IVUV PERL_USE_DEVEL USE_64_BIT_ALL
  USE_64_BIT_INT USE_LARGE_FILES USE_LOCALE
  USE_LOCALE_COLLATE USE_LOCALE_CTYPE
  USE_LOCALE_NUMERIC USE_LOCALE_TIME USE_PERLIO
  USE_PERL_ATOF
  Locally applied patches​:
  uncommitted-changes
  Built under linux
  Compiled at Jan 21 2016 12​:02​:54
  %ENV​:
  PERLBREW_BASHRC_VERSION="0.43"
  PERLBREW_HOME="/home/tony/.perlbrew"
  PERLBREW_PATH="/home/tony/perl5/perlbrew/bin"
  PERLBREW_ROOT="/home/tony/perl5/perlbrew"
  @​INC​:
  lib
  /home/tony/perl/blead/lib/site_perl/5.23.8/x86_64-linux
  /home/tony/perl/blead/lib/site_perl/5.23.8
  /home/tony/perl/blead/lib/5.23.8/x86_64-linux
  /home/tony/perl/blead/lib/5.23.8
  .

[p5pRT]

From @dcollinsn

On Wed Jan 20 17​:14​:21 2016, tonyc wrote​:

This is similar to #127122, but doesn't have quite as simple a fix.

You're right.

I started by looking at what you did for #127122, but the "hack" of treating an unless as an if won't work here. Ultimately, I added a few lines of code to op.c to accept this special case - the condition which currently generates the warning, but with an OP_NOT around it.

I also added a test for this bug to t/lib/warnings/op, as well as a test for the related while(assignment) case, which didn't have a test. The tests reduce to while(0) and until(1) so as to not hang the entire test suite. All tests pass for me.

Patch attached, hopefully formatted correctly.

[p5pRT]

From @dcollinsn

0001-perl-127333-add-warning-for-until-assignment.patch

From 90d93e7911a4471ec779afda1c669a3fe7664d49 Mon Sep 17 00:00:00 2001
From: Dan Collins <dcollinsn@gmail.com>
Date: Mon, 6 Jun 2016 21:04:46 -0400
Subject: [PATCH] [perl #127333] add warning for until(assignment)

while ($a = 1) emits a warning "Found = in conditional, should be ==".
However, until ($a = 1) does not. The parser breaks down until
(condition) into while (!(condition)), which defeats the check in
S_scalarboolean, since it is looking for a conditional that /is/ an
assignment, but we have a conditional that is a thinly veiled assignment.

A similar bug was [perl #127122]. That bug was fixed by treating
unless (a) {b} else {c} as if (a) {c} else {b}, instead of treating it
as if (!a) {b} else {c}. That approach will not work here.

Instead, the test in S_scalarboolean has been widened. It previously
looked for an OP_SASSIGN with op_first OP_CONST, it now also detects an
OP_NOT surrounding that construct.

Tests for both while() and until() were also added to t/lib/warnings/op.
---
 op.c              |  7 +++++--
 t/lib/warnings/op | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/op.c b/op.c
index 619c6e3..9a1f8a4 100644
--- a/op.c
+++ b/op.c
@@ -1532,8 +1532,11 @@ S_scalarboolean(pTHX_ OP *o)
 {
     PERL_ARGS_ASSERT_SCALARBOOLEAN;

-    if (o->op_type == OP_SASSIGN && cBINOPo->op_first->op_type == OP_CONST
-     && !(cBINOPo->op_first->op_flags & OPf_SPECIAL)) {
+    if ((o->op_type == OP_SASSIGN && cBINOPo->op_first->op_type == OP_CONST &&
+         !(cBINOPo->op_first->op_flags & OPf_SPECIAL)) ||
+        (o->op_type == OP_NOT     && cUNOPo->op_first->op_type == OP_SASSIGN &&
+         cBINOPx(cUNOPo->op_first)->op_first->op_type == OP_CONST &&
+         !(cBINOPx(cUNOPo->op_first)->op_first->op_flags & OPf_SPECIAL))) {
        if (ckWARN(WARN_SYNTAX)) {
            const line_t oldline = CopLINE(PL_curcop);

diff --git a/t/lib/warnings/op b/t/lib/warnings/op
index cf7a798..cc0cf46 100644
--- a/t/lib/warnings/op
+++ b/t/lib/warnings/op
@@ -134,6 +134,28 @@ Found = in conditional, should be == at - line 3.
 Found = in conditional, should be == at - line 4.
 ########
 # op.c
+# NAME while with assignment as condition
+use warnings 'syntax';
+1 while $a = 0;
+while ($a = 0) {
+    1;
+}
+EXPECT
+Found = in conditional, should be == at - line 3.
+Found = in conditional, should be == at - line 4.
+########
+# op.c
+# NAME until with assignment as condition
+use warnings 'syntax';
+1 until $a = 1;
+until ($a = 1) {
+    1;
+}
+EXPECT
+Found = in conditional, should be == at - line 3.
+Found = in conditional, should be == at - line 4.
+########
+# op.c
 use warnings 'syntax' ;
 @a[3];
 @a{3};
--
2.8.1

[p5pRT]

The RT System itself - Status changed from 'new' to 'open'

[p5pRT]

From @dcollinsn

Tony reports that that didn't apply. Didn't apply for me either. Probably a line endings issue.

This one should work.

[p5pRT]

From @dcollinsn

0001-perl-127333-add-warning-for-until-assignment.patch

From 9e26b2c7ce3faf108ded08a9d11d3e37a4515a24 Mon Sep 17 00:00:00 2001
From: Dan Collins <dcollinsn@gmail.com>
Date: Mon, 6 Jun 2016 21:04:46 -0400
Subject: [PATCH] [perl #127333] add warning for until(assignment)

while ($a = 1) emits a warning "Found = in conditional, should be ==".
However, until ($a = 1) does not. The parser breaks down until
(condition) into while (!(condition)), which defeats the check in
S_scalarboolean, since it is looking for a conditional that /is/ an
assignment, but we have a conditional that is a thinly veiled assignment.

A similar bug is [perl #127122]. That bug was fixed by treating
unless (a) {b} else {c} as if (a) {c} else {b}, instead of treating it
as if (!a) {b} else {c}. That approach will not work here.

Instead, the test in S_scalarboolean has been widened. It previously
looked for an OP_SASSIGN with op_first OP_CONST, it now also detects an
OP_NOT surrounding that construct.

Tests for both while() and until() were also added to t/lib/warnings/op.
---
 op.c              |  7 +++++--
 t/lib/warnings/op | 22 ++++++++++++++++++++++
 2 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/op.c b/op.c
index 128cdc4..6986610 100644
--- a/op.c
+++ b/op.c
@@ -1532,8 +1532,11 @@ S_scalarboolean(pTHX_ OP *o)
 {
     PERL_ARGS_ASSERT_SCALARBOOLEAN;
 
-    if (o->op_type == OP_SASSIGN && cBINOPo->op_first->op_type == OP_CONST
-     && !(cBINOPo->op_first->op_flags & OPf_SPECIAL)) {
+    if ((o->op_type == OP_SASSIGN && cBINOPo->op_first->op_type == OP_CONST &&
+         !(cBINOPo->op_first->op_flags & OPf_SPECIAL)) ||
+        (o->op_type == OP_NOT     && cUNOPo->op_first->op_type == OP_SASSIGN &&
+         cBINOPx(cUNOPo->op_first)->op_first->op_type == OP_CONST &&
+         !(cBINOPx(cUNOPo->op_first)->op_first->op_flags & OPf_SPECIAL))) {
 	if (ckWARN(WARN_SYNTAX)) {
 	    const line_t oldline = CopLINE(PL_curcop);
 
diff --git a/t/lib/warnings/op b/t/lib/warnings/op
index cf7a798..cc0cf46 100644
--- a/t/lib/warnings/op
+++ b/t/lib/warnings/op
@@ -134,6 +134,28 @@ Found = in conditional, should be == at - line 3.
 Found = in conditional, should be == at - line 4.
 ########
 # op.c
+# NAME while with assignment as condition
+use warnings 'syntax';
+1 while $a = 0;
+while ($a = 0) {
+    1;
+}
+EXPECT
+Found = in conditional, should be == at - line 3.
+Found = in conditional, should be == at - line 4.
+########
+# op.c
+# NAME until with assignment as condition
+use warnings 'syntax';
+1 until $a = 1;
+until ($a = 1) {
+    1;
+}
+EXPECT
+Found = in conditional, should be == at - line 3.
+Found = in conditional, should be == at - line 4.
+########
+# op.c
 use warnings 'syntax' ;
 @a[3];
 @a{3};
-- 
2.8.1

[p5pRT]

From @tonycoz

On Mon Jun 06 19​:17​:37 2016, dcollinsn@​gmail.com wrote​:

Tony reports that that didn't apply. Didn't apply for me either.
Probably a line endings issue.

This one should work.

Thanks, applied as 0a44e30.

Tony

[p5pRT]

@tonycoz - Status changed from 'open' to 'pending release'

[p5pRT]

From @khwilliamson

Thank you for filing this report. You have helped make Perl better.

With the release today of Perl 5.26.0, this and 210 other issues have been
resolved.

Perl 5.26.0 may be downloaded via​:
https://metacpan.org/release/XSAWYERX/perl-5.26.0

If you find that the problem persists, feel free to reopen this ticket.

[p5pRT]

@khwilliamson - Status changed from 'pending release' to 'resolved'