[Bug middle-end/93873] gcc or lto-wrapper does not consider individual bitfield values on static analysis and instead tests the whole value of all bitfield bits combined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93873 --- Comment #4 from Emil Fihlman --- Problem persists with gcc 9.3, though it's no longer dependent on the bitfield. https://godbolt.org/z/RGu6hu If a free is behind a flag.
[Bug middle-end/93873] gcc or lto-wrapper does not consider individual bitfield values on static analysis and instead tests the whole value of all bitfield bits combined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93873 --- Comment #5 from Emil Fihlman --- If a free is behind a flag gcc and the allocation is also behind a flag, gcc should not complain.
[Bug c/93873] New: gcc or lto-wrapper does not consider individual bitfield values on static analysis and instead tests the whole value of all bitfield bits combined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93873
Bug ID: 93873
Summary: gcc or lto-wrapper does not consider individual
bitfield values on static analysis and instead tests
the whole value of all bitfield bits combined
Product: gcc
Version: 6.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: emil.fihlman at aalto dot fi
Target Milestone: ---
On gcc version 6.3.0 20170516 (Debian 6.3.0-18+deb9u1)
Given these two files (and stdtypes.h being available from
https://emil.fi/d/stdtypes.h but it's basically just include stdint.h and
typedef u?int\d+_t to the correct [su]\d+
$cat ltobuglib.h
#include
#include
#include
struct thing
{
u64 v;
struct
{
u64 dox:1;
u64 freeme:1;
} flags;
};
struct thing *makeit(struct thing *t)
{
u8 dynamic=!t;
if(dynamic)
{
t=calloc(1, sizeof(*t));
if(!t)
{
return(NULL);
}
}
t->v=0;
t->flags.dox=1;
t->flags.freeme=dynamic;
return(t);
}
void freeit(struct thing *t)
{
if(t->flags.freeme)
{
free(t);
}
}
$cat ltobug.c
#include
#include
#include "ltobuglib.h"
s32 main(void)
{
struct thing t={0};
if(!makeit(&t))
{
return(-1);
}
printf("%lu %u %u\n", t.v, t.flags.dox, t.flags.freeme);
freeit(&t);
return(0);
}
$gcc -Wall -Werror -Wextra -O3 -flto -o ltobug ltobug.c
produces
In function ‘freeit’,
inlined from ‘main’ at ltobug.c:13:2:
ltobuglib.h:36:3: error: attempt to free a non-heap object ‘t’
[-Werror=free-nonheap-object]
free(t);
^
lto1: all warnings being treated as errors
lto-wrapper: fatal error: gcc returned 1 exit status
compilation terminated.
/usr/bin/ld: error: lto-wrapper failed
collect2: error: ld returned 1 exit status
but changing t->flags.dox=1 to 0 compiles cleanly.
Without -flto (and dox set to 1) the result is
In file included from ltobug.c:3:0:
In function ‘freeit’,
inlined from ‘main’ at ltobug.c:13:2:
ltobuglib.h:36:3: error: attempt to free a non-heap object ‘t’
[-Werror=free-nonheap-object]
free(t);
^~~
cc1: all warnings being treated as errors
On a different project of mine, the code cleanly compiles without -flto (but
fails with -flto as above) but here gcc seems to do the same issue without
-flto, too.
[Bug c/93873] gcc or lto-wrapper does not consider individual bitfield values on static analysis and instead tests the whole value of all bitfield bits combined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93873 --- Comment #1 from Emil Fihlman --- Oh yeah and platform was Linux 4.9.0-8-amd64 #1 SMP Debian 4.9.130-2 (2018-10-27) x86_64 GNU/Linux
[Bug c/91134] New: Confusing error message: error: ‘*server’ is a pointer; did you mean to use ‘->’? when -> is used
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91134 Bug ID: 91134 Summary: Confusing error message: error: ‘*server’ is a pointer; did you mean to use ‘->’? when -> is used Product: gcc Version: 6.3.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: c Assignee: unassigned at gcc dot gnu.org Reporter: emil.fihlman at aalto dot fi Target Milestone: --- gcc -Wall -Werror -Wextra -O3 -flto -o program program.c -lm program.c: In function ‘setupFunction’: program.c:Y:X: error: ‘*server’ is a pointer; did you mean to use ‘->’? if(setupThing(&(*server->thing), MAX_THINGY)==~0UL) ^~ server is of type struct Server ** in this context The error message should probably change in this context to suggesting parentheses. fiesh on #gcc@Freenode gave these ideas regarding this: 2019-07-10 18:11:03 +0300 < fiesh> I think that `server->thing` is probably replaced by `(*server.thing)` since they are semantically equivalent at some stage before the error is produced 2019-07-10 18:11:45 +0300 < fiesh> then the parser sees that *server is a pointer type and you're trying to access its contents with ., so it tells you that doesn't work 2019-07-10 18:12:52 +0300 < fiesh> by ((*server).thing) Emil Using built-in specs. COLLECT_GCC=gcc COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/6/lto-wrapper Target: x86_64-linux-gnu Configured with: ../src/configure -v --with-pkgversion='Debian 6.3.0-18+deb9u1' --with-bugurl=file:///usr/share/doc/gcc-6/README.Bugs --enable-languages=c,ada,c++,java,go,d,fortran,objc,obj-c++ --prefix=/usr --program-suffix=-6 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-libmpx --enable-plugin --enable-default-pie --with-system-zlib --disable-browser-plugin --enable-java-awt=gtk --enable-gtk-cairo --with-java-home=/usr/lib/jvm/java-1.5.0-gcj-6-amd64/jre --enable-java-home --with-jvm-root-dir=/usr/lib/jvm/java-1.5.0-gcj-6-amd64 --with-jvm-jar-dir=/usr/lib/jvm-exports/java-1.5.0-gcj-6-amd64 --with-arch-directory=amd64 --with-ecj-jar=/usr/share/java/eclipse-ecj.jar --with-target-system-zlib --enable-objc-gc=auto --enable-multiarch --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 6.3.0 20170516 (Debian 6.3.0-18+deb9u1)
[Bug c/91134] Confusing error message: error: ‘*server’ is a pointer; did you mean to use ‘->’? when -> is used
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91134 --- Comment #1 from Emil Fihlman --- The fix programming side is of course just wrapping *server in parentheses but the error message should still be amended imho.
