[Bug c/80777] New: long int structure members allocated incorrect 8 bytes

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

Bug ID: 80777
   Summary: long int structure members allocated incorrect 8 bytes
   Product: gcc
   Version: 5.4.0
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c
  Assignee: unassigned at gcc dot gnu.org
  Reporter: jrose.manila at gmail dot com
  Target Milestone: ---

Created attachment 41363
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41363&action=edit
source file describing bug

Problem: long int structure members are allocated incorrect 8 bytes (as if long
long), whereas retyping them with __uint32_t results in correct 4 bytes


$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-pc-cygwin/5.4.0/lto-wrapper.exe
Target: x86_64-pc-cygwin
Configured with:
/cygdrive/i/szsz/tmpp/gcc/gcc-5.4.0-1.x86_64/src/gcc-5.4.0/configure
--srcdir=/cygdrive/i/szsz/tmpp/gcc/gcc-5.4.0-1.x86_64/src/gcc-5.4.0
--prefix=/usr --exec-prefix=/usr --localstatedir=/var --sysconfdir=/etc
--docdir=/usr/share/doc/gcc --htmldir=/usr/share/doc/gcc/html -C
--build=x86_64-pc-cygwin --host=x86_64-pc-cygwin --target=x86_64-pc-cygwin
--without-libiconv-prefix --without-libintl-prefix --libexecdir=/usr/lib
--enable-shared --enable-shared-libgcc --enable-static
--enable-version-specific-runtime-libs --enable-bootstrap --enable-__cxa_atexit
--with-dwarf2 --with-tune=generic
--enable-languages=ada,c,c++,fortran,lto,objc,obj-c++ --enable-graphite
--enable-threads=posix --enable-libatomic --enable-libcilkrts --enable-libgomp
--enable-libitm --enable-libquadmath --enable-libquadmath-support
--enable-libssp --enable-libada --enable-libgcj-sublibs --disable-java-awt
--disable-symvers --with-ecj-jar=/usr/share/java/ecj.jar --with-gnu-ld
--with-gnu-as --with-cloog-include=/usr/include/cloog-isl
--without-libiconv-prefix --without-libintl-prefix --with-system-zlib
--enable-linker-build-id --with-default-libstdcxx-abi=gcc4-compatible
Thread model: posix
gcc version 5.4.0 (GCC)

running on cygwin64 for windows 10:
$ uname -a
CYGWIN_NT-10.0 Caroline-2 2.8.0(0.309/5/3) 2017-04-01 20:47 x86_64 Cygwin


Source: gcc5.4.0.bug.c (attached)
See definition of struct ProductId, members len, format, u.v3.edition.id


How to test:
1. Edit ProductId structure members len, format declarations to either
__uint32_t or unsigned long int
2. gcc -g -Wall -Wextra gcc5.4.0.bug.c -o gcc5.4.0.bug.exe
3. gdb ./gcc5.4.0.bug.exe
b main
b 142
run
c
n
print *pId

and you will see incorrect 8-byte values for pId->len and pId->format if you
declare as unsigned long int, or you will see correct 4-byte values if you
declare with __uint32_t

Further tests within gdb:
print sizeof(long int)
print sizeof(pId->len)
print sizeof(ii)

[Bug c/80777] long int structure members allocated incorrect 8 bytes

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

Julian Rose  changed:

   What|Removed |Added

 Status|RESOLVED|UNCONFIRMED
 Resolution|INVALID |---

--- Comment #2 from Julian Rose  ---
Hei,

Yes I thought that initially too. But if you start gdb and print sizeof(long
int) you get 4, not 8. 

$ gdb
GNU gdb (GDB) (Cygwin 7.10.1-1) 7.10.1
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-cygwin".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
.
Find the GDB manual and other documentation resources online at:
.
For help, type "help".
Type "apropos word" to search for commands related to "word".
(gdb) print sizeof(long int)
$1 = 4
(gdb) print sizeof(unsigned long int)
$2 = 4
(gdb) print sizeof(long long int)
$3 = 8
(gdb) q

[Bug target/80777] gdb reports incorrect sizeof(long int) on x86_64-pc-cygwin

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

Julian Rose  changed:

   What|Removed |Added

Summary|long int structure members  |gdb reports incorrect
   |allocated incorrect 8 bytes |sizeof(long int) on
   ||x86_64-pc-cygwin

--- Comment #3 from Julian Rose  ---
(In reply to Julian Rose from comment #2)
> Hei,
> 
> Yes I thought that initially too. But if you start gdb and print sizeof(long
> int) you get 4, not 8. 
> 
> $ gdb
> GNU gdb (GDB) (Cygwin 7.10.1-1) 7.10.1
> Copyright (C) 2015 Free Software Foundation, Inc.
> License GPLv3+: GNU GPL version 3 or later 
> This is free software: you are free to change and redistribute it.
> There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
> and "show warranty" for details.
> This GDB was configured as "x86_64-pc-cygwin".
> Type "show configuration" for configuration details.
> For bug reporting instructions, please see:
> .
> Find the GDB manual and other documentation resources online at:
> .
> For help, type "help".
> Type "apropos word" to search for commands related to "word".
> (gdb) print sizeof(long int)
> $1 = 4
> (gdb) print sizeof(unsigned long int)
> $2 = 4
> (gdb) print sizeof(long long int)
> $3 = 8
> (gdb) q

But I have changed the summary title of this bug to better reflect that a fault
appears to lie with the gdb build and not with gcc.

Would it be appropriate to close this bug report and raise a new one at
https://sourceware.org/bugzilla/?

[Bug target/80777] gdb sizeof(long int)=4 but gcc sizeof(long int)=8 on x86_64-pc-cygwin

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

Julian Rose  changed:

   What|Removed |Added

Summary|gdb reports incorrect   |gdb sizeof(long int)=4 but
   |sizeof(long int) on |gcc sizeof(long int)=8 on
   |x86_64-pc-cygwin|x86_64-pc-cygwin

--- Comment #4 from Julian Rose  ---
https://software.intel.com/en-us/articles/size-of-long-integer-type-on-different-architecture-and-os
states sizeof long int varies between architectures and operating systems; in
particular sizeof(long) on IA-64 in Linux is 8 whereas in windows it is 4.

Under Cygwin it appears gcc has been built with the "Linux" memory model, and
gdb has been built with the "Windows" model.

Obviously consistency between gcc and gdb is required for any given platform.
But as cygwin runs on a windows platform, it is not clear if the compiler or
the debugger is "wrong". 

Either way, perhaps a solution may be found in the specs configuration given to
the compiler for the x86_64-pc-cygwin platform.

[Bug target/80777] gdb sizeof(long int)=4 but gcc sizeof(long int)=8 on x86_64-pc-cygwin

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

--- Comment #5 from Julian Rose  ---
https://bugzilla.redhat.com/show_bug.cgi?id=518712 describes the same issue
under Linux. But repeating the same test described in comment-1 there when run
under x86_64-pc-cygwin gets the wrong answer:

$ gdb
GNU gdb (GDB) (Cygwin 7.10.1-1) 7.10.1
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later 
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-cygwin".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
.
Find the GDB manual and other documentation resources online at:
.
For help, type "help".
Type "apropos word" to search for commands related to "word".
(gdb) show arch
The target architecture is set automatically (currently i386)
(gdb) set arch
Requires an argument. Valid arguments are i386, i386:x86-64, i386:x64-32,
i8086, i386:intel, i386:x86-64:intel, i386:x64-32:intel, i386:nacl,
i386:x86-64:nacl, i386:x64-32:nacl, auto.
(gdb) set arch i386:x86-64
The target architecture is assumed to be i386:x86-64
(gdb) print sizeof(long)
$1 = 4
(gdb) print sizeof(long long)
$2 = 8
(gdb) print sizeof(long*)
$3 = 8
(gdb) q

[Bug target/80777] gdb sizeof(long int)=4 but gcc sizeof(long int)=8 on x86_64-pc-cygwin

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

--- Comment #9 from Julian Rose  ---
(In reply to Jonathan Wakely from comment #8)
> It uses the ms-abi for calling conventions but LP64, no LLP64:
> https://cygwin.com/cygwin-ug-net/programming.html
> 
> That's by design, and so GCC's behaviour is not a bug. If GDB is
> inconsistent that's not a GCC bug.

Ok, that's good for me. 

Thanks all for the replies. I shall do as comment 6.

[Bug target/80777] gdb sizeof(long int)=4 but gcc sizeof(long int)=8 on x86_64-pc-cygwin

[jrose.manila at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80777

--- Comment #10 from Julian Rose  ---
(In reply to Julian Rose from comment #9)
> (In reply to Jonathan Wakely from comment #8)
> > It uses the ms-abi for calling conventions but LP64, no LLP64:
> > https://cygwin.com/cygwin-ug-net/programming.html
> > 
> > That's by design, and so GCC's behaviour is not a bug. If GDB is
> > inconsistent that's not a GCC bug.
> 
> Ok, that's good for me. 
> 
> Thanks all for the replies. I shall do as comment 6.

https://sourceware.org/bugzilla/show_bug.cgi?id=21500