https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101193
Bug ID: 101193
Summary: [GCOV] Bit operation leads to wrong coverage
information
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: gcov-profile
Assignee: unassigned at gcc dot gnu.org
Reporter: njuwy at smail dot nju.edu.cn
CC: marxin at gcc dot gnu.org
Target Milestone: ---
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/local/libexec/gcc/x86_64-pc-linux-gnu/10.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../configure -enable-checking=release -enable-languages=c,c++
-disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 10.2.0 (GCC)
$ cat test.c
#ifdef __UINT32_TYPE__
typedef __UINT32_TYPE__ uint32_t;
#else
typedef __UINT32_TYPE__ unsigned;
#endif
struct bitfield {
unsigned char f0 : 7;
unsigned char : 1;
unsigned char f1 : 7;
unsigned char : 1;
unsigned char f2 : 7;
unsigned char : 1;
unsigned char f3 : 7;
};
struct ok {
unsigned char f0;
unsigned char f1;
unsigned char f2;
unsigned char f3;
};
union bf_or_uint32 {
struct ok inval;
struct bitfield bfval;
};
__attribute__((noinline, noclone)) uint32_t
partial_read_le32(union bf_or_uint32 in) {
return in.bfval.f0 | (in.bfval.f1 << 8) | (in.bfval.f2 << 16) |
(in.bfval.f3 << 24);
}
int main() {
union bf_or_uint32 bfin;
uint32_t out;
char cin[] = {0x83, 0x85, 0x87, 0x89};
bfin.inval = (struct ok){0x83, 0x85, 0x87, 0x89};
out = partial_read_le32(bfin);
return 0;
}
$ gcc -O0 --coverage test.c;./a.out;gcov test;cat test.c.gcov
File 'test.c'
Lines executed:100.00% of 8
Creating 'test.c.gcov'
-: 0:Source:test.c
-: 0:Graph:test.gcno
-: 0:Data:test.gcda
-: 0:Runs:1
-: 1:#ifdef __UINT32_TYPE__
-: 2:typedef __UINT32_TYPE__ uint32_t;
-: 3:#else
-: 4:typedef __UINT32_TYPE__ unsigned;
-: 5:#endif
-: 6:
-: 7:struct bitfield {
-: 8: unsigned char f0 : 7;
-: 9: unsigned char : 1;
-: 10: unsigned char f1 : 7;
-: 11: unsigned char : 1;
-: 12: unsigned char f2 : 7;
-: 13: unsigned char : 1;
-: 14: unsigned char f3 : 7;
-: 15:};
-: 16:
-: 17:struct ok {
-: 18: unsigned char f0;
-: 19: unsigned char f1;
-: 20: unsigned char f2;
-: 21: unsigned char f3;
-: 22:};
-: 23:
-: 24:union bf_or_uint32 {
-: 25: struct ok inval;
-: 26: struct bitfield bfval;
-: 27:};
-: 28:
-: 29:
-: 30:__attribute__((noinline, noclone)) uint32_t
1: 31:partial_read_le32(union bf_or_uint32 in) {
2: 32: return in.bfval.f0 | (in.bfval.f1 << 8) | (in.bfval.f2 << 16)
|
1: 33: (in.bfval.f3 << 24);
-: 34:}
-: 35:
-: 36:
1: 37:int main() {
-: 38: union bf_or_uint32 bfin;
-: 39: uint32_t out;
1: 40: char cin[] = {0x83, 0x85, 0x87, 0x89};
1: 41: bfin.inval = (struct ok){0x83, 0x85, 0x87, 0x89};
1: 42: out = partial_read_le32(bfin);
-: 43:
-: 44:
1: 45: return 0;
-: 46:}
-: 47:
-: 48:
Line 32 should be executed only once.
