This is a revised part of previously posted patch which
I split up. C FE changes which another false positive
were already merged, but I still need approval for this
middle-end change. It would be nice to get this in,
because it fixes some rather annoying (for me atleast)
false positive warnings with no easy workaround.
In the following example,
int foo(int n, float matrix[n], float opt[n]);
foo(n, matrix, NULL);
GCC warns about NULL iff n > 0. This is problematic for
several reasons:
1. It causes false positives (and I turn off -Wnonnull
in one of my projects for this reason)
2. It is inconsistent with regular arrays where there is no
warning in this case.
3. The size parameter is sometimes shared (as in this example)
so passing zero to avoid the warning is only possible by
making the code more complex.
4. Passing zero as a workaround is technically UB.
(The original author of the warning code, Martin S seemed to
agree with this change according to this discussion in Bugzilla.)
Reduce false positives for -Wnonnull for VLA parameters [PR98541]
This patch limits the warning about NULL arguments to VLA
parameters declared [static n].
PR c/98541
gcc/
* gimple-ssa-warn-access.cc
(pass_waccess::maybe_check_access_sizes): For VLA bounds
in parameters, only warn about null pointers with 'static'.
gcc/testsuite:
* gcc.dg/Wnonnull-4: Adapt test.
* gcc.dg/Wstringop-overflow-40.c: Adapt test.
diff --git a/gcc/gimple-ssa-warn-access.cc b/gcc/gimple-ssa-warn-access.cc
index e439d1b9b68..8b734295f09 100644
--- a/gcc/gimple-ssa-warn-access.cc
+++ b/gcc/gimple-ssa-warn-access.cc
@@ -3477,27 +3477,14 @@ pass_waccess::maybe_check_access_sizes (rdwr_map *rwm,
tree fndecl, tree fntype,
if (integer_zerop (ptr))
{
- if (sizidx >= 0 && tree_int_cst_sgn (sizrng[0]) > 0)
+ if (!access.second.internal_p
+ && sizidx >= 0 && tree_int_cst_sgn (sizrng[0]) > 0)
{
/* Warn about null pointers with positive sizes. This is
different from also declaring the pointer argument with
attribute nonnull when the function accepts null pointers
only when the corresponding size is zero. */
- if (access.second.internal_p)
- {
- const std::string argtypestr
- = access.second.array_as_string (ptrtype);
-
- if (warning_at (loc, OPT_Wnonnull,
- "argument %i of variable length "
- "array %s is null but "
- "the corresponding bound argument "
- "%i value is %s",
- ptridx + 1, argtypestr.c_str (),
- sizidx + 1, sizstr))
- arg_warned = OPT_Wnonnull;
- }
- else if (warning_at (loc, OPT_Wnonnull,
+ if (warning_at (loc, OPT_Wnonnull,
"argument %i is null but "
"the corresponding size argument "
"%i value is %s",
diff --git a/gcc/testsuite/gcc.dg/Wnonnull-4.c
b/gcc/testsuite/gcc.dg/Wnonnull-4.c
index 2c1c45a9856..1f14fbba45d 100644
--- a/gcc/testsuite/gcc.dg/Wnonnull-4.c
+++ b/gcc/testsuite/gcc.dg/Wnonnull-4.c
@@ -27,9 +27,9 @@ void test_fca_n (int r_m1)
T ( 0);
// Verify positive bounds.
- T ( 1); // { dg-warning "argument 2 of variable length array
'char\\\[n]' is null but the corresponding bound argument 1 value is 1" }
- T ( 9); // { dg-warning "argument 2 of variable length array
'char\\\[n]' is null but the corresponding bound argument 1 value is 9" }
- T (max); // { dg-warning "argument 2 of variable length array
'char\\\[n]' is null but the corresponding bound argument 1 value is \\d+" }
+ T ( 1); // { dg-bogus "argument 2 of variable length array
'char\\\[n]' is null but the corresponding bound argument 1 value is 1" }
+ T ( 9); // { dg-bogus "argument 2 of variable length array
'char\\\[n]' is null but the corresponding bound argument 1 value is 9" }
+ T (max); // { dg-bogus "argument 2 of variable length array
'char\\\[n]' is null but the corresponding bound argument 1 value is \\d+" }
}
@@ -55,9 +55,9 @@ void test_fsa_x_n (int r_m1)
T ( 0);
// Verify positive bounds.
- T ( 1); // { dg-warning "argument 2 of variable length array
'short int\\\[]\\\[n]' is null but the corresponding bound argument 1 value is
1" }
- T ( 9); // { dg-warning "argument 2 of variable length array
'short int\\\[]\\\[n]' is null but the corresponding bound argument 1 value is
9" }
- T (max); // { dg-warning "argument 2 of variable length array
'short int\\\[]\\\[n]' is null but the corresponding bound argument 1 value is
\\d+" }
+ T ( 1); // { dg-bogus "argument 2 of variable length array 'short
int\\\[]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
+ T ( 9); // { dg-bogus "argument 2 of variable length array 'short
int\\\[]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
+ T (max); // { dg-bogus "argument 2 of variable length array 'short
int\\\[]\\\[n]' is null but the corresponding bound argument 1 value is \\d+" }
}
@@ -83,9 +83,9 @@ void test_fia_1_n (int r_m1)
T ( 0);
// Verify positive bounds.
- T ( 1); // { dg-warning "argument 2 of variable length array
'int\\\[1]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
- T ( 9); // { dg-warning "argument 2 of variable length array
'int\\\[1]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
- T (max); // { dg-warning "argument 2 of variable length array
'int\\\[1]\\\[n]' is null but the corresponding bound argument 1 value is \\d+"
}
+ T ( 1); // { dg-bogus "argument 2 of variable length array
'int\\\[1]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
+ T ( 9); // { dg-bogus "argument 2 of variable length array
'int\\\[1]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
+ T (max); // { dg-bogus "argument 2 of variable length array
'int\\\[1]\\\[n]' is null but the corresponding bound argument 1 value is \\d+"
}
}
@@ -111,9 +111,9 @@ void test_fla_3_n (int r_m1)
T ( 0);
// Verify positive bounds.
- T ( 1); // { dg-warning "argument 2 of variable length array 'long
int\\\[3]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
- T ( 9); // { dg-warning "argument 2 of variable length array 'long
int\\\[3]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
- T (max); // { dg-warning "argument 2 of variable length array 'long
int\\\[3]\\\[n]' is null but the corresponding bound argument 1 value is \\d+" }
+ T ( 1); // { dg-bogus "argument 2 of variable length array 'long
int\\\[3]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
+ T ( 9); // { dg-bogus "argument 2 of variable length array 'long
int\\\[3]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
+ T (max); // { dg-bogus "argument 2 of variable length array 'long
int\\\[3]\\\[n]' is null but the corresponding bound argument 1 value is \\d+" }
}
@@ -139,9 +139,9 @@ void test_fda_n_5 (int r_m1)
T ( 0);
// Verify positive bounds.
- T ( 1); // { dg-warning "argument 2 of variable length array
'double\\\[n]\\\[5]' is null but the corresponding bound argument 1 value is 1"
}
- T ( 9); // { dg-warning "argument 2 of variable length array
'double\\\[n]\\\[5]' is null but the corresponding bound argument 1 value is 9"
}
- T (max); // { dg-warning "argument 2 of variable length array
'double\\\[n]\\\[5]' is null but the corresponding bound argument 1 value is
\\d+" }
+ T ( 1); // { dg-bogus "argument 2 of variable length array
'double\\\[n]\\\[5]' is null but the corresponding bound argument 1 value is 1"
}
+ T ( 9); // { dg-bogus "argument 2 of variable length array
'double\\\[n]\\\[5]' is null but the corresponding bound argument 1 value is 9"
}
+ T (max); // { dg-bogus "argument 2 of variable length array
'double\\\[n]\\\[5]' is null but the corresponding bound argument 1 value is
\\d+" }
}
@@ -167,7 +167,7 @@ void test_fca_n_n (int r_m1)
T ( 0);
// Verify positive bounds.
- T ( 1); // { dg-warning "argument 2 of variable length array
'char\\\[n]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
- T ( 9); // { dg-warning "argument 2 of variable length array
'char\\\[n]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
- T (max); // { dg-warning "argument 2 of variable length array
'char\\\[n]\\\[n]' is null but the corresponding bound argument 1 value is
\\d+" }
+ T ( 1); // { dg-bogus "argument 2 of variable length array
'char\\\[n]\\\[n]' is null but the corresponding bound argument 1 value is 1" }
+ T ( 9); // { dg-bogus "argument 2 of variable length array
'char\\\[n]\\\[n]' is null but the corresponding bound argument 1 value is 9" }
+ T (max); // { dg-bogus "argument 2 of variable length array
'char\\\[n]\\\[n]' is null but the corresponding bound argument 1 value is
\\d+" }
}
diff --git a/gcc/testsuite/gcc.dg/Wstringop-overflow-40.c
b/gcc/testsuite/gcc.dg/Wstringop-overflow-40.c
index 386c92dc7a8..9e0ad1f3aff 100644
--- a/gcc/testsuite/gcc.dg/Wstringop-overflow-40.c
+++ b/gcc/testsuite/gcc.dg/Wstringop-overflow-40.c
@@ -11,6 +11,7 @@ void fxa2 (int16_t[2]) __attribute__ ((nonnull));
void fas2 (int16_t[static 2]);
void fvla (unsigned n, int16_t[n]);
+void fvlaS (unsigned n, int16_t[static n]);
void test_array_1_dim (void)
{
@@ -33,7 +34,8 @@ void test_array_1_dim (void)
fas2 (a1); // { dg-warning "'fas2' accessing 4 bytes in a
region of size 2 " }
fas2 (&i); // { dg-warning "'fas2' accessing 4 bytes in a
region of size 2 " }
- fvla (1, 0); // { dg-warning "\\\[-Wnonnull" }
+ fvla (1, 0);
+ fvlaS (1, 0); // { dg-warning "\\\[-Wnonnull" }
fvla (1, &i);
fvla (2, a2);
fvla (2, a1); // { dg-warning "'fvla' accessing 4 bytes in a
region of size 2 " }
@@ -47,6 +49,7 @@ void fxac2 (const int16_t[2]) __attribute__ ((nonnull));
void facs2 (const int16_t[static 2]);
void fvlac (unsigned n, const int16_t[n]);
+void fvlacS (unsigned n, const int16_t[static n]);
void test_const_array_1_dim (void)
{
@@ -69,7 +72,8 @@ void test_const_array_1_dim (void)
facs2 (a1); // { dg-warning "'facs2' reading 4 bytes from a
region of size 2 " }
facs2 (&i); // { dg-warning "'facs2' reading 4 bytes from a
region of size 2 " }
- fvlac (1, 0); // { dg-warning "\\\[-Wnonnull" }
+ fvlac (1, 0);
+ fvlacS (1, 0); // { dg-warning "\\\[-Wnonnull" }
fvlac (1, &i);
fvlac (2, a2);
fvlac (2, a1); // { dg-warning "'fvlac' reading 4 bytes from a
region of size 2 " }
