On 27/04/11 03:42, David Holmes wrote:
Hi Joe,
I sent email to coin-dev on this yesterday but it doesn't seem to have
turned up - at least I haven't seen it.
In some cases at least these catch clauses are in fact reachable -
e.g. ThreadPoolExecutor. The analysis assumes that checked-exceptions
can only be thrown by methods that declare them, but we all know that
is not the case: Class.newInstance and native methods can throw them
too (are there other cases?). So sometimes we want the "unreachable"
catch as a "safety-net" for these cases.
Given checked-exception checks can be circumvented it seems to me that
the analysis should not be issuing warnings for these cases because it
will encourage people to "fix the code" - as you have just asked to be
done! - when in fact the code could be less robust if it is changed.
I see your concerns - unfortunately there is no way to statically
distinguish 'good' cases from 'bad' cases - i.e. a call to
Class.newInstance could be hidden behind a method called inside the
try-block. So, it seems like the only sensible option would be to
special case 'catch(Throwable)'.
Maurizio
Cheers,
David
Joe Darcy said the following on 04/27/11 11:53:
Hello.
FYI, javac in JDK 7 does a more precise analysis than before on what
catch blocks can actually be reached and warnings are issued for
unreachable catch blocks. I've extracted those warnings from a
recent full JDK build in case anyone wants to update the code in
question.
-Joe
../../../../../../src/share/classes/com/sun/corba/se/impl/protocol/BootstrapServerRequestDispatcher.java:124:
warning: unreachable catch clause
} catch (java.lang.Exception ex) {
^
thrown type RuntimeException has already been caught
../../../../../../src/share/classes/com/sun/corba/se/impl/protocol/BootstrapServerRequestDispatcher.java:124:
warning: unreachable catch clause
} catch (java.lang.Exception ex) {
^
thrown type RuntimeException has already been caught
../../../src/share/classes/java/util/concurrent/ThreadPoolExecutor.java:1115:
warning: unreachable catch clause
} catch (Throwable x) {
^
thrown types RuntimeException,Error have already been caught
../../../src/share/classes/java/net/DatagramSocket.java:183: warning:
unreachable catch clause
} catch(IOException e) {
^
thrown type SocketException has already been caught
Note: Some input files use or override a deprecated API.
Note: Recompile with -Xlint:deprecation for details.
Note: Some input files use unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.
2 warnings
../../../src/share/classes/java/security/cert/X509CertSelector.java:2217:
warning: unreachable catch clause
} catch (CertificateException e3) {
^
thrown types
CertificateNotYetValidException,CertificateExpiredException have
already been caught
../../../src/share/classes/javax/management/modelmbean/RequiredModelMBean.java:1220:
warning: unreachable catch clause
} catch (Exception e) {
^
thrown types
InvocationTargetException,IllegalAccessException,RuntimeException
have already been caught
1 warning
../../../../src/share/classes/sun/security/rsa/RSASignature.java:205:
warning: unreachable catch clause
} catch (GeneralSecurityException e) {
^
thrown type BadPaddingException has already been caught
