http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55428
Bug #: 55428
Summary: -mms-bitfields hides -mno-align-double option
Classification: Unclassified
Product: gcc
Version: 4.6.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: kasber...@heidenhain.de
i686-pc-linux-gbu-gcc -mno-align-double -mms-bitfields test.cpp
("-mno-align-double" is the equivalent to /zp4)
This command line ignores the "-mno-align-double" option.
With -mno-align-double standalone it will do the correct double alignments but
no the ms bitfield alignment (What is expected)
If I add -mms-bitfields the alignment for bitfields will be correct but the
"-mno-align-double" is now gone
Here the program I have tested. Is it possible to achieve binary compatibility
to ms compiler with option /zp4 enabled
i686-pc-linux-gbu-gcc -mno-align-double -mms-bitfields test.cpp
test.cpp:48:58: warning: large integer implicitly truncated to unsigned type
[-Woverflow]
test.cpp:54:54: warning: large integer implicitly truncated to unsigned type
[-Woverflow]
i686-pc-linux-gbu-gcc -mno-align-double test.cpp
test.cpp:52:53: warning: large integer implicitly truncated to unsigned type
[-Woverflow]
test.cpp:58:53: warning: large integer implicitly truncated to unsigned type
[-Woverflow]
i686-pc-linux-gbu-gcc -mms-bitfields test.cpp
test.cpp:48:58: warning: large integer implicitly truncated to unsigned type
[-Woverflow]
test.cpp:54:54: warning: large integer implicitly truncated to unsigned type
[-Woverflow]
// 8
typedef struct _jhtest1 {
unsigned long bf_1 : 12;
unsigned long : 0;
unsigned long bf_2 : 12;
} jhtest1;
//??
typedef struct _jhtest2 {
char foo : 4;
short : 0;
char bar;
} jhtest2;
//??
typedef struct _jhtest3 {
char foo : 4;
short : 0;
double bar;
} jhtest3;
//4
typedef struct _jhtest4 {
char foo : 6;
long : 0;
} jhtest4;
// 2
typedef struct _jhtest5 {
char foo;
long : 0;
char bar;
} jhtest5;
typedef struct _jhtest {
double xx;
char y;
double yy;
long z;
} jhtest;
unsigned char jh_double = (sizeof (double) == 8 )?1:1111111;
unsigned char jh_test0 = (sizeof (jhtest) == (8*2+8) )?1:1111111;
unsigned char jh_test1 = (sizeof (jhtest1) == 8 )?1:1111111;
unsigned char jh_test2 = (sizeof (jhtest2) == 4 )?1:1111111; // VC++
unsigned char jh_test3 = (sizeof (jhtest3) == 12 )?1:1111111;
unsigned char jh_test4 = (sizeof (jhtest4) == 4 )?1:1111111;
unsigned char jh_test5 = (sizeof (jhtest5) == 2 )?1:1111111; // VC++
int main()
{
}
