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GCC4 cleanup question

KJ Chuck Short 4 participants 4 messages May 28, 2005 – May 30, 2005 Kernel janitors

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Chuck Short

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#0 lore raw

Hi,

I was wondering how would you fix warnings like the following:

net/ipv4/route.c: In function 'ip_route_input_slow':
net/ipv4/route.c:1770: warning: 'rth' may be used uninitialized in this functionnet/ipv4/route.c:1797: warning: 'rth' may be used uninitialized in this functionnet/ipv4/route.c: In function 'ip_route_output_slow':
net/ipv4/route.c:2270: warning: 'rth' may be used uninitialized in this functionnet/ipv4/route.c:2242: warning: 'rth' may be used uninitialized in this function

Thanks
chuck
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#1 lore raw
Quoted 12 lines · Chuck Short

Hi,

I was wondering how would you fix warnings like the following:

net/ipv4/route.c: In function 'ip_route_input_slow':
net/ipv4/route.c:1770: warning: 'rth' may be used uninitialized in this functionnet/ipv4/route.c:1797: warning: 'rth' may be used uninitialized in this functionnet/ipv4/route.c: In function 'ip_route_output_slow':
net/ipv4/route.c:2270: warning: 'rth' may be used uninitialized in this functionnet/ipv4/route.c:2242: warning: 'rth' may be used uninitialized in this function

Quoted 2 lines

Thanks
chuck

I don't have GCC4, the first rth is initialised inside the __mkroute_input function and the second one is initialised in the __mkroute_output function. I don't know why gcc is giving those warings.

ipv4/route.c 2005-05-28 08:23:18.000000000 +0200 renamed from ipv4/route.c.old 2005-05-18 21:18:19.000000000 +0200 +2 -2
@@ -1767,7 +1767,7 @@ static inline int ip_mkroute_input_def(s
                                       struct in_device *in_dev,
                                       u32 daddr, u32 saddr, u32 tos)
 {
-       struct rtable* rth;
+       struct rtable* rth = NULL;
        int err;
        unsigned hash;
 

@@ -2267,7 +2267,7 @@ static inline int ip_mkroute_output(stru
        unsigned char hop;
        unsigned hash;
        int err = -EINVAL;
-       struct rtable *rth;
+       struct rtable *rth = NULL;
 
        if (res->fi && res->fi->fib_nhs > 1) {
                unsigned char hopcount = res->fi->fib_nhs;

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#2 lore raw
In reply to Chuck Short

Quoting Bongani Hlope <[email protected]>
Sent on Sat, 28 May 2005 08:25:54 +0200

Quoted 3 lines

I don't have GCC4, the first rth is initialised inside the __mkroute_input function and the second one is initialised in the __mkroute_output function. I don't know why gcc is giving those warings.

My guess is because it doesn't know/see that. Wouldn't that be related to the new interprocedural optimization?

More info, perhaps starting on:

http://gcc.gnu.org/wiki/Interprocedural%20optimizations

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Ricardo Nabinger Sanchez
GNU/Linux #140696 [http://counter.li.org]
Slackware Linux + FreeBSD

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#3 lore raw
In reply to Chuck Short
Quoted 3 lines · Bongani Hlope

I don't have GCC4, the first rth is initialised inside the __mkroute_input function and the second one is initialised in the __mkroute_output function. I don't know why gcc is giving those warings.

__mkroute_{in,out}put does not initialize *result if it returns early.

ipv4/route.c    2005-05-28 08:23:18.000000000 +0200 static inline int ip_mkroute_input_def(s · line 1773

Quoted 11 lines
ipv4/route.c    2005-05-28 08:23:18.000000000 +0200 renamed from ipv4/route.c.old        2005-05-18 21:18:19.000000000 +0200 +1 -1
@@ -1767,7 +1767,7 @@ static inline int ip_mkroute_input_def(s
                                        struct in_device *in_dev,
                                        u32 daddr, u32 saddr, u32 tos)
  {
-       struct rtable* rth;
+       struct rtable* rth = NULL;
         int err;
         unsigned hash;

We've already had that discussion. Don't initialize it to a bogus value in the declaration, but make sure it always gets set in the function that is responsible for initializing it (__mkroute_input in this case).

	Arnd <><

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