https://gcc.gnu.org/bugzilla/show_bug.cgi?id=89469
Bug ID: 89469
Summary: [GCOV] wrong frequencies for the first statement in
the for(;;) block
Product: gcc
Version: 8.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: gcov-profile
Assignee: unassigned at gcc dot gnu.org
Reporter: yangyibiao at nju dot edu.cn
CC: marxin at gcc dot gnu.org
Target Milestone: ---
$ gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/8/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu
8.2.0-1ubuntu2~18.04' --with-bugurl=file:///usr/share/doc/gcc-8/README.Bugs
--enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++ --prefix=/usr
--with-gcc-major-version-only --program-suffix=-8
--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 --with-target-system-zlib --enable-objc-gc=auto
--enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64
--with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic
--enable-offload-targets=nvptx-none --without-cuda-driver
--enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu
--target=x86_64-linux-gnu
Thread model: posix
gcc version 8.2.0 (Ubuntu 8.2.0-1ubuntu2~18.04)
$ cat small.c
int main()
{
int start = 0, mid = 3, limit = 3, lastMid = 6, r = 0;
for (;;) {
mid = (start + limit) / 2;
if (lastMid == mid) {
break;
}
r = mid == 1 ? 1 : 0;
if (r > 0) {
start = mid;
} else {
return 1;
}
}
return 0;
}
$ gcc -O0 --coverage small.c -w; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:80.00% of 10
Creating 'small.c.gcov'
-: 0:Source:small.c
-: 0:Graph:small.gcno
-: 0:Data:small.gcda
-: 0:Runs:1
-: 0:Programs:1
1: 1:int main()
-: 2:{
1: 3: int start = 0, mid = 3, limit = 3, lastMid = 6, r = 0;
-: 4: for (;;) {
1: 5: mid = (start + limit) / 2;
2: 6: if (lastMid == mid) {
#####: 7: break;
-: 8: }
-: 9:
2: 10: r = mid == 1 ? 1 : 0;
-: 11:
2: 12: if (r > 0) {
1: 13: start = mid;
-: 14: } else {
1: 15: return 1;
-: 16: }
-: 17: }
#####: 18: return 0;
-: 19:}
Line #5 is wrongly marked as executed once which should be executed twice.
When Line #7 is removed, the result is correct as:
$ gcc -O0 --coverage small.c -w; ./a.out; gcov small.c; cat small.c.gcov
File 'small.c'
Lines executed:100.00% of 7
Creating 'small.c.gcov'
-: 0:Source:small.c
-: 0:Graph:small.gcno
-: 0:Data:small.gcda
-: 0:Runs:1
-: 0:Programs:1
1: 1:int main()
-: 2:{
1: 3: int start = 0, mid = 3, limit = 3, lastMid = 6, r = 0;
-: 4: for (;;) {
2: 5: mid = (start + limit) / 2;
-: 6: if (lastMid == mid) {
-: 7: // break;
-: 8: }
-: 9:
2: 10: r = mid == 1 ? 1 : 0;
-: 11:
2: 12: if (r > 0) {
1: 13: start = mid;
-: 14: } else {
1: 15: return 1;
-: 16: }
-: 17: }
-: 18: return 0;
-: 19:}
