Re: c++/1833: [2003-01-01] inlining sometimes causes incorrect behavior

[Nigel Stewart <nigels@nigels.com>]

The following reply was made to PR c++/1833; it has been noted by GNATS.

From: Nigel Stewart <nigels@nigels.com>
To: gcc-gnats@gcc.gnu.org,  gcc-bugs@gcc.gnu.org,  nobody@gcc.gnu.org, 
 gcc-prs@gcc.gnu.org,  peteb@sitera.com
Cc:  
Subject: Re: c++/1833: [2003-01-01] inlining sometimes causes incorrect behavior
Date: Fri, 04 Apr 2003 03:24:48 +1000

 http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=1833
 
 Perhaps the bug/problem/issue I've found in gcc is related to this one
 already in the database: Problem Report 1833
 
 -------
 
 #include <iostream>
 using namespace std;
 
 float foo()
 {
 	assert(sizeof(unsigned int)==sizeof(float));
 	
 	float tmp = 0.0;
 	*((unsigned int *) &tmp) = (127<<23) | (1<<22);
 	
 	return tmp;
 }
 
 int main(int argc,char *argv[])
 {
 	cout << "Output should be 1.5: " << foo() << endl;
 }
 
 -------
 
 $ gcc -v
 Reading specs from /usr/lib/gcc-lib/i686-pc-cygwin/3.2/specs
 Configured with: /netrel/src/gcc-3.2-3/configure --enable-languages=c,c++,f77,java --enable-libgcj --enable-threads=posix --with-system-zlib --enable-nls --without-included-gettext --enable-interpreter --disable-sjlj-exceptions --disable-version-specific-runtime-libs --enable-shared --build=i686-pc-linux --host=i686-pc-cygwin --target=i686-pc-cygwin --enable-haifa --prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --libdir=/usr/lib --includedir=/nonexistent/include --libexecdir=/usr/sbin
 Thread model: posix
 gcc version 3.2 20020927 (prerelease)
 
 $ g++ test.cpp -o test && ./test
 Output should be 1.5: 1.5
 
 $ g++ -O2 test.cpp -o test && ./test
 Output should be 1.5: 0
 
 --------
 
 The following version of foo does not exhibit the same problem:
 
 float foo()
 {
 	assert(sizeof(unsigned int)==sizeof(float));
 
 	unsigned int tmp = (127<<23) | (1<<22);
 	return *((float *) &tmp);
 }
 
 Regards,
 
 Nigel Stewart
 nigels@nigels.com