| Message ID | 577E1156.2030604@linux.vnet.ibm.com |
|---|---|
| State | Superseded |
| Headers | show |
PING On 07/07/2016 10:22 AM, Stefan Liebler wrote: > Hi, > > while testing, I've got the following werror on s390x when build with > gcc 6.1 (or current gcc head) and -O3: > ../sysdeps/ieee754/dbl-64/k_rem_pio2.c: In function ‘__kernel_rem_pio2’: > ../sysdeps/ieee754/dbl-64/k_rem_pio2.c:254:18: error: array subscript is > below array bounds [-Werror=array-bounds] > for (k = 1; iq[jk - k] == 0; k++) > ~~^~~~~~~~ > > I get the same error with sysdeps/ieee754/flt-32/k_rem_pio2f.c. > > Does anybody else get this warning on another architecture, too? > > This patch adds a check so that the index is always >= 0. > Afterwards glibc builds/tests fine with gcc 6.1 and -O3. > > Okay to commit? > Before or after release? > > Bye > Stefan > > ChangeLog: > > * sysdeps/ieee754/dbl-64/k_rem_pio2.c (__kernel_rem_pio2): > Add test to ensure that array-index is >= 0. > * sysdeps/ieee754/flt-32/k_rem_pio2f.c (__kernel_rem_pio2f): > Likewise.
PING On 07/13/2016 12:25 PM, Stefan Liebler wrote: > PING > > On 07/07/2016 10:22 AM, Stefan Liebler wrote: >> Hi, >> >> while testing, I've got the following werror on s390x when build with >> gcc 6.1 (or current gcc head) and -O3: >> ../sysdeps/ieee754/dbl-64/k_rem_pio2.c: In function ‘__kernel_rem_pio2’: >> ../sysdeps/ieee754/dbl-64/k_rem_pio2.c:254:18: error: array subscript is >> below array bounds [-Werror=array-bounds] >> for (k = 1; iq[jk - k] == 0; k++) >> ~~^~~~~~~~ >> >> I get the same error with sysdeps/ieee754/flt-32/k_rem_pio2f.c. >> >> Does anybody else get this warning on another architecture, too? >> >> This patch adds a check so that the index is always >= 0. >> Afterwards glibc builds/tests fine with gcc 6.1 and -O3. >> >> Okay to commit? >> Before or after release? >> >> Bye >> Stefan >> >> ChangeLog: >> >> * sysdeps/ieee754/dbl-64/k_rem_pio2.c (__kernel_rem_pio2): >> Add test to ensure that array-index is >= 0. >> * sysdeps/ieee754/flt-32/k_rem_pio2f.c (__kernel_rem_pio2f): >> Likewise. > >
On Thu, 7 Jul 2016, Stefan Liebler wrote: > Hi, > > while testing, I've got the following werror on s390x when build with gcc 6.1 > (or current gcc head) and -O3: > ../sysdeps/ieee754/dbl-64/k_rem_pio2.c: In function ‘__kernel_rem_pio2’: > ../sysdeps/ieee754/dbl-64/k_rem_pio2.c:254:18: error: array subscript is below > array bounds [-Werror=array-bounds] > for (k = 1; iq[jk - k] == 0; k++) > ~~^~~~~~~~ > > I get the same error with sysdeps/ieee754/flt-32/k_rem_pio2f.c. > > Does anybody else get this warning on another architecture, too? > > This patch adds a check so that the index is always >= 0. Such an unnecessary check is not how we deal with bogus warnings. Rather, use the DIAG_*_NEEDS_COMMENT macros from include/libc-internal.h, with a detailed comment explaining what the warning is and why it is a false positive.
diff --git a/sysdeps/ieee754/dbl-64/k_rem_pio2.c b/sysdeps/ieee754/dbl-64/k_rem_pio2.c index e58c9e8..4fe14de 100644 --- a/sysdeps/ieee754/dbl-64/k_rem_pio2.c +++ b/sysdeps/ieee754/dbl-64/k_rem_pio2.c @@ -251,7 +251,7 @@ recompute: j |= iq[i]; if (j == 0) /* need recomputation */ { - for (k = 1; iq[jk - k] == 0; k++) + for (k = 1; k <= jk && iq[jk - k] == 0; k++) ; /* k = no. of terms needed */ for (i = jz + 1; i <= jz + k; i++) /* add q[jz+1] to q[jz+k] */ diff --git a/sysdeps/ieee754/flt-32/k_rem_pio2f.c b/sysdeps/ieee754/flt-32/k_rem_pio2f.c index 392afdb..805f487 100644 --- a/sysdeps/ieee754/flt-32/k_rem_pio2f.c +++ b/sysdeps/ieee754/flt-32/k_rem_pio2f.c @@ -122,7 +122,8 @@ recompute: j = 0; for (i=jz-1;i>=jk;i--) j |= iq[i]; if(j==0) { /* need recomputation */ - for(k=1;iq[jk-k]==0;k++); /* k = no. of terms needed */ + for (k = 1; k <= jk && iq[jk - k] == 0; k++) + ; /* k = no. of terms needed */ for(i=jz+1;i<=jz+k;i++) { /* add q[jz+1] to q[jz+k] */ f[jx+i] = (float) ipio2[jv+i];
Hi, while testing, I've got the following werror on s390x when build with gcc 6.1 (or current gcc head) and -O3: ../sysdeps/ieee754/dbl-64/k_rem_pio2.c: In function ‘__kernel_rem_pio2’: ../sysdeps/ieee754/dbl-64/k_rem_pio2.c:254:18: error: array subscript is below array bounds [-Werror=array-bounds] for (k = 1; iq[jk - k] == 0; k++) ~~^~~~~~~~ I get the same error with sysdeps/ieee754/flt-32/k_rem_pio2f.c. Does anybody else get this warning on another architecture, too? This patch adds a check so that the index is always >= 0. Afterwards glibc builds/tests fine with gcc 6.1 and -O3. Okay to commit? Before or after release? Bye Stefan ChangeLog: * sysdeps/ieee754/dbl-64/k_rem_pio2.c (__kernel_rem_pio2): Add test to ensure that array-index is >= 0. * sysdeps/ieee754/flt-32/k_rem_pio2f.c (__kernel_rem_pio2f): Likewise.