Re: [Qemu-devel] [PATCH V2] build: remove compile warning

[Wenchao Xia]

于 2013-6-18 18:13, Paolo Bonzini 写道:
Il 07/06/2013 14:17, Markus Armbruster ha scritto:
diff --git a/util/iov.c b/util/iov.c
index cc6e837..b91cfb9 100644
--- a/util/iov.c
+++ b/util/iov.c
@@ -146,7 +146,7 @@ ssize_t iov_send_recv(int sockfd, struct iovec *iov, 
unsigned iov_cnt,
  {
      ssize_t total = 0;
      ssize_t ret;
-    size_t orig_len, tail;
+    size_t orig_len = 0, tail;
      unsigned niov;
      while (bytes > 0) {

Here are the uses of orig_len:

         if (tail) {
             /* second, fixup the last element, and remember the original
              * length */
             assert(niov < iov_cnt);
             assert(iov[niov].iov_len > tail);
             orig_len = iov[niov].iov_len;
             iov[niov++].iov_len = tail;
         }

         ret = do_send_recv(sockfd, iov, niov, do_send);

         /* Undo the changes above before checking for errors */
         if (tail) {
             iov[niov-1].iov_len = orig_len;
         }


gcc is too stupid to understand the control flow.  The initialization
shuts it up.

Looks like most people's GCC is not that stupid, or I would have broken
build for everyone, right?

Paolo


my gcc version:
[xiawenc@RH63Wenchao ~]$ gcc -v
Using built-in specs.
Target: x86_64-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man 
--infodir=/usr/share/info 
--with-bugurl=http://bugzilla.redhat.com/bugzilla --enable-bootstrap 
--enable-shared --enable-threads=posix --enable-checking=release 
--with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions 
--enable-gnu-unique-object 
--enable-languages=c,c++,objc,obj-c++,java,fortran,ada 
--enable-java-awt=gtk --disable-dssi 
--with-java-home=/usr/lib/jvm/java-1.5.0-gcj-1.5.0.0/jre 
--enable-libgcj-multifile --enable-java-maintainer-mode 
--with-ecj-jar=/usr/share/java/eclipse-ecj.jar 
--disable-libjava-multilib --with-ppl --with-cloog --with-tune=generic 
--with-arch_32=i686 --build=x86_64-redhat-linux
Thread model: posix
gcc version 4.4.6 20120305 (Red Hat 4.4.6-4) (GCC)


  By default configure, it seems qemu didn't set -Werror to break build.
--
Best Regards

Wenchao Xia