checkpatch.pl

			($dstat, $dcond, $ln, $cnt, $off) =
				ctx_statement_block($linenr, $realcnt, 0);
			$ctx = $dstat;

			$dstat =~ s/\\\n.//g;

			if ($dstat =~ /^\+\s*#\s*define\s+$Ident\s*${balanced_parens}\s*do\s*{(.*)\s*}\s*while\s*\(\s*0\s*\)\s*([;\s]*)\s*$/) {
				my $stmts = $2;
				my $semis = $3;

				$ctx =~ s/\n*$//;
				my $cnt = statement_rawlines($ctx);
				my $herectx = $here . "\n";

				for (my $n = 0; $n < $cnt; $n++) {
					$herectx .= raw_line($linenr, $n) . "\n";
				}

				if (($stmts =~ tr/;/;/) == 1) {
					WARN("SINGLE_STATEMENT_DO_WHILE_MACRO",
					     "Single statement macros should not use a do {} while (0) loop\n" . "$herectx");
				}
				if (defined $semis && $semis ne "") {
					WARN("DO_WHILE_MACRO_WITH_TRAILING_SEMICOLON",
					     "do {} while (0) macros should not be semicolon terminated\n" . "$herectx");
				}
			}
		}

# make sure symbols are always wrapped with VMLINUX_SYMBOL() ...
# all assignments may have only one of the following with an assignment:
#	.
#	ALIGN(...)
#	VMLINUX_SYMBOL(...)
		if ($realfile eq 'vmlinux.lds.h' && $line =~ /(?:(?:^|\s)$Ident\s*=|=\s*$Ident(?:\s|$))/) {
			WARN("MISSING_VMLINUX_SYMBOL",
			     "vmlinux.lds.h needs VMLINUX_SYMBOL() around C-visible symbols\n" . $herecurr);
		}

# check for redundant bracing round if etc
		if ($line =~ /(^.*)\bif\b/ && $1 !~ /else\s*$/) {
			my ($level, $endln, @chunks) =
				ctx_statement_full($linenr, $realcnt, 1);
			#print "chunks<$#chunks> linenr<$linenr> endln<$endln> level<$level>\n";
			#print "APW: <<$chunks[1][0]>><<$chunks[1][1]>>\n";
			if ($#chunks > 0 && $level == 0) {
				my @allowed = ();
				my $allow = 0;
				my $seen = 0;
				my $herectx = $here . "\n";
				my $ln = $linenr - 1;
				for my $chunk (@chunks) {
					my ($cond, $block) = @{$chunk};

					# If the condition carries leading newlines, then count those as offsets.
					my ($whitespace) = ($cond =~ /^((?:\s*\n[+-])*\s*)/s);
					my $offset = statement_rawlines($whitespace) - 1;

					$allowed[$allow] = 0;
					#print "COND<$cond> whitespace<$whitespace> offset<$offset>\n";

					# We have looked at and allowed this specific line.
					$suppress_ifbraces{$ln + $offset} = 1;

					$herectx .= "$rawlines[$ln + $offset]\n[...]\n";
					$ln += statement_rawlines($block) - 1;

					substr($block, 0, length($cond), '');

					$seen++ if ($block =~ /^\s*{/);

					#print "cond<$cond> block<$block> allowed<$allowed[$allow]>\n";
					if (statement_lines($cond) > 1) {
						#print "APW: ALLOWED: cond<$cond>\n";
						$allowed[$allow] = 1;
					}
					if ($block =~/\b(?:if|for|while)\b/) {
						#print "APW: ALLOWED: block<$block>\n";
						$allowed[$allow] = 1;
					}
					if (statement_block_size($block) > 1) {
						#print "APW: ALLOWED: lines block<$block>\n";
						$allowed[$allow] = 1;
					}
					$allow++;
				}
				if ($seen) {
					my $sum_allowed = 0;
					foreach (@allowed) {
						$sum_allowed += $_;
					}
					if ($sum_allowed == 0) {
						WARN("BRACES",
						     "braces {} are not necessary for any arm of this statement\n" . $herectx);
					} elsif ($sum_allowed != $allow &&
						 $seen != $allow) {
						CHK("BRACES",
						    "braces {} should be used on all arms of this statement\n" . $herectx);
					}
				}
			}
		}
		if (!defined $suppress_ifbraces{$linenr - 1} &&
					$line =~ /\b(if|while|for|else)\b/) {
			my $allowed = 0;

			# Check the pre-context.
			if (substr($line, 0, $-[0]) =~ /(\}\s*)$/) {
				#print "APW: ALLOWED: pre<$1>\n";
				$allowed = 1;
			}

			my ($level, $endln, @chunks) =
				ctx_statement_full($linenr, $realcnt, $-[0]);

			# Check the condition.
			my ($cond, $block) = @{$chunks[0]};
			#print "CHECKING<$linenr> cond<$cond> block<$block>\n";
			if (defined $cond) {
				substr($block, 0, length($cond), '');
			}
			if (statement_lines($cond) > 1) {
				#print "APW: ALLOWED: cond<$cond>\n";
				$allowed = 1;
			}
			if ($block =~/\b(?:if|for|while)\b/) {
				#print "APW: ALLOWED: block<$block>\n";
				$allowed = 1;
			}
			if (statement_block_size($block) > 1) {
				#print "APW: ALLOWED: lines block<$block>\n";
				$allowed = 1;
			}
			# Check the post-context.
			if (defined $chunks[1]) {
				my ($cond, $block) = @{$chunks[1]};
				if (defined $cond) {
					substr($block, 0, length($cond), '');
				}
				if ($block =~ /^\s*\{/) {
					#print "APW: ALLOWED: chunk-1 block<$block>\n";
					$allowed = 1;
				}
			}
			if ($level == 0 && $block =~ /^\s*\{/ && !$allowed) {
				my $herectx = $here . "\n";
				my $cnt = statement_rawlines($block);

				for (my $n = 0; $n < $cnt; $n++) {
					$herectx .= raw_line($linenr, $n) . "\n";
				}

				WARN("BRACES",
				     "braces {} are not necessary for single statement blocks\n" . $herectx);
			}
		}

# don't include deprecated include files (uses RAW line)
		for my $inc (@dep_includes) {
			if ($rawline =~ m@^.\s*\#\s*include\s*\<$inc>@) {
				ERROR("DEPRECATED_INCLUDE",
				      "Don't use <$inc>: see Documentation/feature-removal-schedule.txt\n" . $herecurr);
			}
		}

# don't use deprecated functions
		for my $func (@dep_functions) {
			if ($line =~ /\b$func\b/) {
				ERROR("DEPRECATED_FUNCTION",
				      "Don't use $func(): see Documentation/feature-removal-schedule.txt\n" . $herecurr);
			}
		}

# no volatiles please
		my $asm_volatile = qr{\b(__asm__|asm)\s+(__volatile__|volatile)\b};
		if ($line =~ /\bvolatile\b/ && $line !~ /$asm_volatile/) {
			WARN("VOLATILE",
			     "Use of volatile is usually wrong: see Documentation/volatile-considered-harmful.txt\n" . $herecurr);
		}

# warn about #if 0
		if ($line =~ /^.\s*\#\s*if\s+0\b/) {
			CHK("REDUNDANT_CODE",
			    "if this code is redundant consider removing it\n" .
				$herecurr);
		}

# check for needless kfree() checks
		if ($prevline =~ /\bif\s*\(([^\)]*)\)/) {
			my $expr = $1;
			if ($line =~ /\bkfree\(\Q$expr\E\);/) {
				WARN("NEEDLESS_KFREE",
				     "kfree(NULL) is safe this check is probably not required\n" . $hereprev);
			}
		}
# check for needless usb_free_urb() checks
		if ($prevline =~ /\bif\s*\(([^\)]*)\)/) {
			my $expr = $1;
			if ($line =~ /\busb_free_urb\(\Q$expr\E\);/) {
				WARN("NEEDLESS_USB_FREE_URB",
				     "usb_free_urb(NULL) is safe this check is probably not required\n" . $hereprev);
			}
		}

# prefer usleep_range over udelay
		if ($line =~ /\budelay\s*\(\s*(\w+)\s*\)/) {
			# ignore udelay's < 10, however
			if (! (($1 =~ /(\d+)/) && ($1 < 10)) ) {
				CHK("USLEEP_RANGE",
				    "usleep_range is preferred over udelay; see Documentation/timers/timers-howto.txt\n" . $line);
			}
		}

# warn about unexpectedly long msleep's
		if ($line =~ /\bmsleep\s*\((\d+)\);/) {
			if ($1 < 20) {
				WARN("MSLEEP",
				     "msleep < 20ms can sleep for up to 20ms; see Documentation/timers/timers-howto.txt\n" . $line);
			}
		}

# warn about #ifdefs in C files
#		if ($line =~ /^.\s*\#\s*if(|n)def/ && ($realfile =~ /\.c$/)) {
#			print "#ifdef in C files should be avoided\n";
#			print "$herecurr";
#			$clean = 0;
#		}

# warn about spacing in #ifdefs
		if ($line =~ /^.\s*\#\s*(ifdef|ifndef|elif)\s\s+/) {
			ERROR("SPACING",
			      "exactly one space required after that #$1\n" . $herecurr);
		}

# check for spinlock_t definitions without a comment.
		if ($line =~ /^.\s*(struct\s+mutex|spinlock_t)\s+\S+;/ ||
		    $line =~ /^.\s*(DEFINE_MUTEX)\s*\(/) {
			my $which = $1;
			if (!ctx_has_comment($first_line, $linenr)) {
				CHK("UNCOMMENTED_DEFINITION",
				    "$1 definition without comment\n" . $herecurr);
			}
		}
# check for memory barriers without a comment.
		if ($line =~ /\b(mb|rmb|wmb|read_barrier_depends|smp_mb|smp_rmb|smp_wmb|smp_read_barrier_depends)\(/) {
			if (!ctx_has_comment($first_line, $linenr)) {
				CHK("MEMORY_BARRIER",
				    "memory barrier without comment\n" . $herecurr);
			}
		}
# check of hardware specific defines
		if ($line =~ m@^.\s*\#\s*if.*\b(__i386__|__powerpc64__|__sun__|__s390x__)\b@ && $realfile !~ m@include/asm-@) {
			CHK("ARCH_DEFINES",
			    "architecture specific defines should be avoided\n" .  $herecurr);
		}

# Check that the storage class is at the beginning of a declaration
		if ($line =~ /\b$Storage\b/ && $line !~ /^.\s*$Storage\b/) {
			WARN("STORAGE_CLASS",
			     "storage class should be at the beginning of the declaration\n" . $herecurr)
		}

# check the location of the inline attribute, that it is between
# storage class and type.
		if ($line =~ /\b$Type\s+$Inline\b/ ||
		    $line =~ /\b$Inline\s+$Storage\b/) {
			ERROR("INLINE_LOCATION",
			      "inline keyword should sit between storage class and type\n" . $herecurr);
		}

# Check for __inline__ and __inline, prefer inline
		if ($line =~ /\b(__inline__|__inline)\b/) {
			WARN("INLINE",
			     "plain inline is preferred over $1\n" . $herecurr);
		}

# Check for __attribute__ packed, prefer __packed
		if ($line =~ /\b__attribute__\s*\(\s*\(.*\bpacked\b/) {
			WARN("PREFER_PACKED",
			     "__packed is preferred over __attribute__((packed))\n" . $herecurr);
		}

# Check for __attribute__ aligned, prefer __aligned
		if ($line =~ /\b__attribute__\s*\(\s*\(.*aligned/) {
			WARN("PREFER_ALIGNED",
			     "__aligned(size) is preferred over __attribute__((aligned(size)))\n" . $herecurr);
		}

# Check for __attribute__ format(printf, prefer __printf
		if ($line =~ /\b__attribute__\s*\(\s*\(\s*format\s*\(\s*printf/) {
			WARN("PREFER_PRINTF",
			     "__printf(string-index, first-to-check) is preferred over __attribute__((format(printf, string-index, first-to-check)))\n" . $herecurr);
		}

# Check for __attribute__ format(scanf, prefer __scanf
		if ($line =~ /\b__attribute__\s*\(\s*\(\s*format\s*\(\s*scanf\b/) {
			WARN("PREFER_SCANF",
			     "__scanf(string-index, first-to-check) is preferred over __attribute__((format(scanf, string-index, first-to-check)))\n" . $herecurr);
		}

# check for sizeof(&)
		if ($line =~ /\bsizeof\s*\(\s*\&/) {
			WARN("SIZEOF_ADDRESS",
			     "sizeof(& should be avoided\n" . $herecurr);
		}

# check for sizeof without parenthesis
		if ($line =~ /\bsizeof\s+((?:\*\s*|)$Lval|$Type(?:\s+$Lval|))/) {
			WARN("SIZEOF_PARENTHESIS",
			     "sizeof $1 should be sizeof($1)\n" . $herecurr);
		}

# check for line continuations in quoted strings with odd counts of "
		if ($rawline =~ /\\$/ && $rawline =~ tr/"/"/ % 2) {
			WARN("LINE_CONTINUATIONS",
			     "Avoid line continuations in quoted strings\n" . $herecurr);
		}

# Check for misused memsets
		if ($^V && $^V ge 5.10.0 &&
		    defined $stat &&
		    $stat =~ /^\+(?:.*?)\bmemset\s*\(\s*$FuncArg\s*,\s*$FuncArg\s*\,\s*$FuncArg\s*\)/s) {

			my $ms_addr = $2;
			my $ms_val = $7;
			my $ms_size = $12;

			if ($ms_size =~ /^(0x|)0$/i) {
				ERROR("MEMSET",
				      "memset to 0's uses 0 as the 2nd argument, not the 3rd\n" . "$here\n$stat\n");
			} elsif ($ms_size =~ /^(0x|)1$/i) {
				WARN("MEMSET",
				     "single byte memset is suspicious. Swapped 2nd/3rd argument?\n" . "$here\n$stat\n");
			}
		}

# typecasts on min/max could be min_t/max_t
		if ($^V && $^V ge 5.10.0 &&
		    defined $stat &&
		    $stat =~ /^\+(?:.*?)\b(min|max)\s*\(\s*$FuncArg\s*,\s*$FuncArg\s*\)/) {
			if (defined $2 || defined $7) {
				my $call = $1;
				my $cast1 = deparenthesize($2);
				my $arg1 = $3;
				my $cast2 = deparenthesize($7);
				my $arg2 = $8;
				my $cast;

				if ($cast1 ne "" && $cast2 ne "" && $cast1 ne $cast2) {
					$cast = "$cast1 or $cast2";
				} elsif ($cast1 ne "") {
					$cast = $cast1;
				} else {
					$cast = $cast2;
				}
				WARN("MINMAX",
				     "$call() should probably be ${call}_t($cast, $arg1, $arg2)\n" . "$here\n$stat\n");
			}
		}

# check usleep_range arguments
		if ($^V && $^V ge 5.10.0 &&
		    defined $stat &&
		    $stat =~ /^\+(?:.*?)\busleep_range\s*\(\s*($FuncArg)\s*,\s*($FuncArg)\s*\)/) {
			my $min = $1;
			my $max = $7;
			if ($min eq $max) {
				WARN("USLEEP_RANGE",
				     "usleep_range should not use min == max args; see Documentation/timers/timers-howto.txt\n" . "$here\n$stat\n");
			} elsif ($min =~ /^\d+$/ && $max =~ /^\d+$/ &&
				 $min > $max) {
				WARN("USLEEP_RANGE",
				     "usleep_range args reversed, use min then max; see Documentation/timers/timers-howto.txt\n" . "$here\n$stat\n");
			}
		}

# check for new externs in .c files.
		if ($realfile =~ /\.c$/ && defined $stat &&
		    $stat =~ /^.\s*(?:extern\s+)?$Type\s+($Ident)(\s*)\(/s)
		{
			my $function_name = $1;
			my $paren_space = $2;

			my $s = $stat;
			if (defined $cond) {
				substr($s, 0, length($cond), '');
			}
			if ($s =~ /^\s*;/ &&
			    $function_name ne 'uninitialized_var')
			{
				WARN("AVOID_EXTERNS",
				     "externs should be avoided in .c files\n" .  $herecurr);
			}

			if ($paren_space =~ /\n/) {
				WARN("FUNCTION_ARGUMENTS",
				     "arguments for function declarations should follow identifier\n" . $herecurr);
			}

		} elsif ($realfile =~ /\.c$/ && defined $stat &&
		    $stat =~ /^.\s*extern\s+/)
		{
			WARN("AVOID_EXTERNS",
			     "externs should be avoided in .c files\n" .  $herecurr);
		}

# checks for new __setup's
		if ($rawline =~ /\b__setup\("([^"]*)"/) {
			my $name = $1;

			if (!grep(/$name/, @setup_docs)) {
				CHK("UNDOCUMENTED_SETUP",
				    "__setup appears un-documented -- check Documentation/kernel-parameters.txt\n" . $herecurr);
			}
		}

# check for pointless casting of kmalloc return
		if ($line =~ /\*\s*\)\s*[kv][czm]alloc(_node){0,1}\b/) {
			WARN("UNNECESSARY_CASTS",
			     "unnecessary cast may hide bugs, see http://c-faq.com/malloc/mallocnocast.html\n" . $herecurr);
		}

# check for multiple semicolons
		if ($line =~ /;\s*;\s*$/) {
		    WARN("ONE_SEMICOLON",
			 "Statements terminations use 1 semicolon\n" . $herecurr);
		}

# check for gcc specific __FUNCTION__
		if ($line =~ /__FUNCTION__/) {
			WARN("USE_FUNC",
			     "__func__ should be used instead of gcc specific __FUNCTION__\n"  . $herecurr);
		}

# check for use of yield()
		if ($line =~ /\byield\s*\(\s*\)/) {
			WARN("YIELD",
			     "Using yield() is generally wrong. See yield() kernel-doc (sched/core.c)\n"  . $herecurr);
		}

# check for semaphores initialized locked
		if ($line =~ /^.\s*sema_init.+,\W?0\W?\)/) {
			WARN("CONSIDER_COMPLETION",
			     "consider using a completion\n" . $herecurr);
		}

# recommend kstrto* over simple_strto* and strict_strto*
		if ($line =~ /\b((simple|strict)_(strto(l|ll|ul|ull)))\s*\(/) {
			WARN("CONSIDER_KSTRTO",
			     "$1 is obsolete, use k$3 instead\n" . $herecurr);
		}

# check for __initcall(), use device_initcall() explicitly please
		if ($line =~ /^.\s*__initcall\s*\(/) {
			WARN("USE_DEVICE_INITCALL",
			     "please use device_initcall() instead of __initcall()\n" . $herecurr);
		}

# check for various ops structs, ensure they are const.
		my $struct_ops = qr{acpi_dock_ops|
				address_space_operations|
				backlight_ops|
				block_device_operations|
				dentry_operations|
				dev_pm_ops|
				dma_map_ops|
				extent_io_ops|
				file_lock_operations|
				file_operations|
				hv_ops|
				ide_dma_ops|
				intel_dvo_dev_ops|
				item_operations|
				iwl_ops|
				kgdb_arch|
				kgdb_io|
				kset_uevent_ops|
				lock_manager_operations|
				microcode_ops|
				mtrr_ops|
				neigh_ops|
				nlmsvc_binding|
				pci_raw_ops|
				pipe_buf_operations|
				platform_hibernation_ops|
				platform_suspend_ops|
				proto_ops|
				rpc_pipe_ops|
				seq_operations|
				snd_ac97_build_ops|
				soc_pcmcia_socket_ops|
				stacktrace_ops|
				sysfs_ops|
				tty_operations|
				usb_mon_operations|
				wd_ops}x;
		if ($line !~ /\bconst\b/ &&
		    $line =~ /\bstruct\s+($struct_ops)\b/) {
			WARN("CONST_STRUCT",
			     "struct $1 should normally be const\n" .
				$herecurr);
		}

# use of NR_CPUS is usually wrong
# ignore definitions of NR_CPUS and usage to define arrays as likely right
		if ($line =~ /\bNR_CPUS\b/ &&
		    $line !~ /^.\s*\s*#\s*if\b.*\bNR_CPUS\b/ &&
		    $line !~ /^.\s*\s*#\s*define\b.*\bNR_CPUS\b/ &&
		    $line !~ /^.\s*$Declare\s.*\[[^\]]*NR_CPUS[^\]]*\]/ &&
		    $line !~ /\[[^\]]*\.\.\.[^\]]*NR_CPUS[^\]]*\]/ &&
		    $line !~ /\[[^\]]*NR_CPUS[^\]]*\.\.\.[^\]]*\]/)
		{
			WARN("NR_CPUS",
			     "usage of NR_CPUS is often wrong - consider using cpu_possible(), num_possible_cpus(), for_each_possible_cpu(), etc\n" . $herecurr);
		}

# check for %L{u,d,i} in strings
		my $string;
		while ($line =~ /(?:^|")([X\t]*)(?:"|$)/g) {
			$string = substr($rawline, $-[1], $+[1] - $-[1]);
			$string =~ s/%%/__/g;
			if ($string =~ /(?<!%)%L[udi]/) {
				WARN("PRINTF_L",
				     "\%Ld/%Lu are not-standard C, use %lld/%llu\n" . $herecurr);
				last;
			}
		}

# whine mightly about in_atomic
		if ($line =~ /\bin_atomic\s*\(/) {
			if ($realfile =~ m@^drivers/@) {
				ERROR("IN_ATOMIC",
				      "do not use in_atomic in drivers\n" . $herecurr);
			} elsif ($realfile !~ m@^kernel/@) {
				WARN("IN_ATOMIC",
				     "use of in_atomic() is incorrect outside core kernel code\n" . $herecurr);
			}
		}

# check for lockdep_set_novalidate_class
		if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
		    $line =~ /__lockdep_no_validate__\s*\)/ ) {
			if ($realfile !~ m@^kernel/lockdep@ &&
			    $realfile !~ m@^include/linux/lockdep@ &&
			    $realfile !~ m@^drivers/base/core@) {
				ERROR("LOCKDEP",
				      "lockdep_no_validate class is reserved for device->mutex.\n" . $herecurr);
			}
		}

		if ($line =~ /debugfs_create_file.*S_IWUGO/ ||
		    $line =~ /DEVICE_ATTR.*S_IWUGO/ ) {
			WARN("EXPORTED_WORLD_WRITABLE",
			     "Exporting world writable files is usually an error. Consider more restrictive permissions.\n" . $herecurr);
		}
	}

	# If we have no input at all, then there is nothing to report on
	# so just keep quiet.
	if ($#rawlines == -1) {
		exit(0);
	}

	# In mailback mode only produce a report in the negative, for
	# things that appear to be patches.
	if ($mailback && ($clean == 1 || !$is_patch)) {
		exit(0);
	}

	# This is not a patch, and we are are in 'no-patch' mode so
	# just keep quiet.
	if (!$chk_patch && !$is_patch) {
		exit(0);
	}

	if (!$is_patch) {
		ERROR("NOT_UNIFIED_DIFF",
		      "Does not appear to be a unified-diff format patch\n");
	}
	if ($is_patch && $chk_signoff && $signoff == 0) {
		ERROR("MISSING_SIGN_OFF",
		      "Missing Signed-off-by: line(s)\n");
	}

	print report_dump();
	if ($summary && !($clean == 1 && $quiet == 1)) {
		print "$filename " if ($summary_file);
		print "total: $cnt_error errors, $cnt_warn warnings, " .
			(($check)? "$cnt_chk checks, " : "") .
			"$cnt_lines lines checked\n";
		print "\n" if ($quiet == 0);
	}

	if ($quiet == 0) {

		if ($^V lt 5.10.0) {
			print("NOTE: perl $^V is not modern enough to detect all possible issues.\n");
			print("An upgrade to at least perl v5.10.0 is suggested.\n\n");
		}

		# If there were whitespace errors which cleanpatch can fix
		# then suggest that.
		if ($rpt_cleaners) {
			print "NOTE: whitespace errors detected, you may wish to use scripts/cleanpatch or\n";
			print "      scripts/cleanfile\n\n";
			$rpt_cleaners = 0;
		}
	}

	if ($quiet == 0 && keys %ignore_type) {
	    print "NOTE: Ignored message types:";
	    foreach my $ignore (sort keys %ignore_type) {
		print " $ignore";
	    }
	    print "\n\n";
	}

	if ($clean == 1 && $quiet == 0) {
		print "$vname has no obvious style problems and is ready for submission.\n"
	}
	if ($clean == 0 && $quiet == 0) {
		print << "EOM";
$vname has style problems, please review.

If any of these errors are false positives, please report
them to the maintainer, see CHECKPATCH in MAINTAINERS.
EOM
	}

	return $clean;
}