From mboxrd@z Thu Jan  1 00:00:00 1970
From: elfring@users.sourceforge.net (SF Markus Elfring)
Date: Mon, 20 Jul 2015 13:31:40 +0200
Subject: [Cocci] Finding unstored return values with SmPL
In-Reply-To: <alpine.DEB.2.02.1507181351130.2042@localhost6.localdomain6>
References: <55A62135.90206@users.sourceforge.net>
 <alpine.DEB.2.10.1507150629540.2670@hadrien>
 <55AA3B1F.5020807@users.sourceforge.net>
 <alpine.DEB.2.02.1507181351130.2042@localhost6.localdomain6>
Message-ID: <55ACDC1C.1040005@users.sourceforge.net>
To: cocci@systeme.lip6.fr
List-Id: cocci@systeme.lip6.fr

> Do you really need to use a regular expression here?
> Why not use a disjunction in the pattern?

Another source code analysis approach like the following might make
the involved software design decisions a bit more clear.


@show_unstored_return_values@
identifier allocation =~ "^(?x)
(?:
   pthread_mutex_(?:try|un)?lock
|
   sigaction
)$", structure_var, var, work;
field element;
struct structure_type;
type data_type, return_type;
@@
 return_type work(...)
 {
  <+...
(
  data_type var = allocation(...);
|
  structure_type structure_var = { ... .element = allocation(...) ... };
|
(
  var
|
  structure_var
)
  = allocation(...)
|
* (void) allocation(...);
|
* allocation(...)
)
  ...+>
 }


elfring at Sonne:~/Projekte/Coccinelle/janitor> spatch.opt -sp-file show_unstored_return_values2.cocci unchecked_return_values1.c
init_defs_builtins: /usr/local/lib/coccinelle/standard.h
181 182
Fatal error: exception Failure("meta: parse error: \n = File \"show_unstored_return_values2.cocci\", line 9, column 21,  charpos = 181\n    around = ';', whole content = struct structure_type;\n")


How can this "surprise" be fixed?



> How is it useful to match just thf function call.

Does the following small source code example contain a few update candidates
for further considerations?

#include <pthread.h>

static pthread_mutex_t my_lock = PTHREAD_MUTEX_INITIALIZER;
static unsigned long my_counter = 1;

void increment_a_shared_variable(void)
{
 pthread_mutex_lock(&my_lock);
 ++my_counter;
 pthread_mutex_unlock(&my_lock);
}



> This doesn't show anything about whether or not the return value is stored.

Does the following SmPL script draft show another interesting application
of the semantic patch language?

@show_unstored_return_values@
identifier allocation =~ "^(?x)
(?:
   pthread_mutex_(?:try|un)?lock
|
   sigaction
)$", var, work;
type data_type, return_type;
@@
 return_type work(...)
 {
  <+...
(
  data_type var = allocation(...);
|
  var = allocation(...)
|
* (void) allocation(...);
|
* allocation(...)
)
  ...+>
 }


elfring at Sonne:~/Projekte/Coccinelle/janitor> spatch.opt -sp-file show_unstored_return_values3.cocci unchecked_return_values1.c
init_defs_builtins: /usr/local/lib/coccinelle/standard.h
HANDLING: unchecked_return_values1.c
diff = 
--- unchecked_return_values1.c
+++ /tmp/cocci-output-7564-385170-unchecked_return_values1.c
@@ -5,7 +5,5 @@ static unsigned long my_counter = 1;
 
 void increment_a_shared_variable(void)
 {
- pthread_mutex_lock(&my_lock);
  ++my_counter;
- pthread_mutex_unlock(&my_lock);
 }


How do you think about my imaginations for corresponding software improvements?

Regards,
Markus