On Mon, 2015-04-20 at 11:33 +0300, Dan Carpenter wrote: > You would hope that GCC would warn about the uninitialized variable but > it doesn't. That's odd. So I filed this new gcc bugzilla: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65812) gcc 4.9.1 doesn't warn about uninitialized variable use declared in a switch/case statement when compiled with -O Here is a small example: $ cat t.c struct foo { int bar[100]; }; void foo_1(void) { unsigned int m; extern struct foo *array[100]; struct foo *a = array[m]; a = a; } void foo_2(void) { int i = 1; switch (i) { case 1: { unsigned int m; extern struct foo *array[100]; struct foo *a = array[m]; a = a; break; } } } $ gcc warns properly about both foo_1 and foo_2 without -O $ gcc -c -Wall t.c t.c: In function ‘foo_1’: t.c:9:14: warning: ‘m’ is used uninitialized in this function [-Wuninitialized] struct foo *a = array[m]; ^ t.c: In function ‘foo_2’: t.c:21:15: warning: ‘m’ may be used uninitialized in this function [-Wmaybe-uninitialized] struct foo *a = array[m]; ^ $ but gcc warns about foo_1 but not foo_2 with -O $ gcc -c -Wall -O t.c t.c: In function ‘foo_1’: t.c:9:14: warning: ‘m’ is used uninitialized in this function [-Wuninitialized] struct foo *a = array[m]; ^ $ gcc -v Using built-in specs. COLLECT_GCC=/usr/bin/gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.9/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Ubuntu 4.9.1-16ubuntu6' --with-bugurl=file:///usr/share/doc/gcc-4.9/README.Bugs --enable-languages=c,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-4.9 --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.9 --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-4.9-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-4.9-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --enable-objc-gc --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu Thread model: posix gcc version 4.9.1 (Ubuntu 4.9.1-16ubuntu6) _______________________________________________ devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxx http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
