[Bug c++/109260] New: -fdump-ada-spec does not support C++ namespaces
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109260
Bug ID: 109260
Summary: -fdump-ada-spec does not support C++ namespaces
Product: gcc
Version: 12.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
For example, the following C++ code has three namespaces:
namespace test_ns
{
namespace test_ns_1
{
struct A_Record { int x, y; };
}
namespace test_ns_2
{
struct A_Record { int x, y, z; };
}
}
Using g++ -fdump-ada-spec generates the following package, which has
declaration conflicts:
package test_ns_hh is
type A_Record is record
x : aliased int; -- test_ns.hh:5
y : aliased int; -- test_ns.hh:5
end record
with Convention => C_Pass_By_Copy; -- test_ns.hh:5
type A_Record is record
x : aliased int; -- test_ns.hh:10
y : aliased int; -- test_ns.hh:10
z : aliased int; -- test_ns.hh:10
end record
with Convention => C_Pass_By_Copy; -- test_ns.hh:10
end test_ns_hh;
[Bug c/102909] Missing -Wunused-but-set-variable warning
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102909 --- Comment #3 from Iru Cai --- Looks like this kind of things are detected in the front-end. The GNAT front-end can warn on the similar things: procedure Main is A : Integer; B : constant Integer := 1; begin A := 0; A := A + B; end Main; $ gcc -O2 -gnatwa -gnatwe -c main.adb main.adb:6:09: warning: possibly useless assignment to "A", value might not be referenced
[Bug c/102909] Missing -Wunused-but-set-variable warning
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102909 --- Comment #2 from Iru Cai --- So it looks something like https://gcc.gnu.org/bugzilla/show_bug.cgi?id=44677 GCC thinks ``a`` is set but not used in ``a = 1 + b;``, but is used in ``a = 1; a += b;``.
[Bug c/102909] New: Missing -Wunused-but-set-variable warning
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102909
Bug ID: 102909
Summary: Missing -Wunused-but-set-variable warning
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
GCC misses the -Wunused-but-set-variable in the some code (GCC and Clang output
can be seen in https://godbolt.org/z/7658M4qra).
I first found a bug caused by the following code, in which no compilers warn:
void ioapic_set_max_vectors(void *ioapic_base, int mre_count)
{
u32 reg;
u8 count;
reg = io_apic_read(ioapic_base, 0x01);
count = reg >> 16;
if (mre_count > 0)
count = mre_count - 1;
// reg is defined but not used after this
reg &= ~(0xff << 16);
reg |= count << 16;
// ``count`` should be ``reg`` in the following line
io_apic_write(ioapic_base, 0x01, count);
}
I think that's because the variable ``reg`` is only unused in part of the
control flow, so I change the code as following. However, GCC doesn't warn on
this either.
void ioapic_set_max_vectors(void *ioapic_base, int mre_count)
{
u32 reg;
u32 new_reg;
u8 count;
reg = io_apic_read(ioapic_base, 0x01);
count = reg >> 16;
if (mre_count > 0)
count = mre_count - 1;
// new_reg is defined but not used
new_reg = reg & (~(0xff << 16));
new_reg |= count << 16;
// ``count`` should be ``new_reg`` in the following
io_apic_write(ioapic_base, 0x01, count);
}
[Bug other/102495] New: optimize some consecutive byte load pattern to word load
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102495
Bug ID: 102495
Summary: optimize some consecutive byte load pattern to word
load
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
I use the following code get a 32-bit word from a byte array by loading each
byte and shifting them, but GCC doesn't optimize the code to a single word load
when I put the byte load in a loop.
Clang trunk can optimize all of the follows:
https://gcc.godbolt.org/z/KfWE67K5c
```
#define SHL(a,b) ((uint32_t)(a) << (b))
// both GCC and Clang optimize to *(uint32_t*)(vv)
uint32_t getword_b(const uint8_t *vv)
{
return SHL(vv[3], 24) | SHL(vv[2], 16) | SHL(vv[1], 8) | SHL(vv[0], 0);
}
// GCC cannot optimize this, Clang can
uint32_t getword_forloop(const uint8_t *vv)
{
uint32_t res = 0;
for (size_t i = 0; i < 4; i++) {
res |= SHL(vv[i], (i * 8));
}
return res;
}
// both GCC and Clang optimize to ((uint32_t*)(vec))[word_idx]
uint32_t getword_from_vec(const uint8_t *vec, size_t word_idx)
{
size_t byte_idx = word_idx * 4;
const uint8_t *vv = vec + byte_idx;
return SHL(vv[3], 24) | SHL(vv[2], 16) | SHL(vv[1], 8) | SHL(vv[0], 0);
}
// neither GCC nor Clang 12.0.1 can optimize this, Clang trunk can
uint32_t getword_from_vec_forloop(const uint8_t *vec, size_t word_idx)
{
size_t byte_idx = word_idx * 4;
uint32_t res = 0;
for (size_t i = 0; i < 4; i++) {
res |= SHL(vec[byte_idx + i], (i * 8));
}
return res;
}
```
[Bug c++/101775] New: G++ drops namespace prefix of argument in the referenced function symbol
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101775
Bug ID: 101775
Summary: G++ drops namespace prefix of argument in the
referenced function symbol
Product: gcc
Version: 11.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
When g++ builds following code, the function foo() referenced by this program
is compiled to symbol ``foo(VecReg&)``, which should be ``foo(MyISA::VecReg&)``
with the namespace prefix. This results in a linking error.
```
// test.cc
#include
#include
namespace MyISA {
typedef struct {
uint8_t data[64];
} VecReg;
}
void foo(MyISA::VecReg );
using MyISA::VecReg;
class A
{
VecReg v;
public:
void test();
};
typedef MyISA::VecReg VecReg;
void A::test()
{
foo(v);
}
int main()
{
A a;
a.test();
}
```
```
// foo.cc
#include
namespace MyISA {
typedef struct {
uint8_t data[64];
} VecReg;
}
void foo(MyISA::VecReg )
{
v.data[0] = 42;
}
```
$ g++ -c test.cc ; g++ -c foo.cc ; g++ -o main test.o foo.o
/usr/bin/ld: test.o: in function `A::test()':
test.cc:(.text+0x14): undefined reference to `foo(VecReg&)'
$ nm -C test.o foo.o
test.o:
U _GLOBAL_OFFSET_TABLE_
001b T main
U __stack_chk_fail
U foo(VecReg&)
T A::test()
foo.o:
T foo(MyISA::VecReg&)
[Bug ada/101385] -Werror doesn't have effect on Ada frontend
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101385 --- Comment #2 from Iru Cai --- Thanks, -gnatwe works for both gcc and gnatmake. I see in the gnat_ugn manual that there is still the -Werror option that causes GCC back end to treat warnings as errors. Is that means -gnatwe is for front end, and -Werror for back end?
[Bug ada/101385] New: -Werror doesn't have effect on Ada frontend
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101385 Bug ID: 101385 Summary: -Werror doesn't have effect on Ada frontend Product: gcc Version: 11.1.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: ada Assignee: unassigned at gcc dot gnu.org Reporter: mytbk920423 at gmail dot com Target Milestone: --- I try to make the GCC Ada compiler error when there're warnings, but -Werror doesn't work. $ gcc -c -O2 -Werror test.adb && echo "Command returns $?" test.adb:3:22: warning: value not in range of type "MyChar" defined at line 2 test.adb:3:22: warning: "Constraint_Error" will be raised at run time Command returns 0 $ gnatmake test.adb -cargs -Werror && echo "Command returns $?" gcc -c -Werror test.adb test.adb:3:22: warning: value not in range of type "MyChar" defined at line 2 test.adb:3:22: warning: "Constraint_Error" will be raised at run time gnatbind -x test.ali gnatlink test.ali gnatlink: warning: executable name "test" may conflict with shell command Command returns 0
[Bug target/101175] New: builtin_clz generates wrong bsr instruction
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=101175
Bug ID: 101175
Summary: builtin_clz generates wrong bsr instruction
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
Built with '-march=x86-64-v3 -O1', the following code generates a bsr
instruction, which has undefined behavior when the source operand is zero, thus
gives wrong result (code also in https://gcc.godbolt.org/z/zzT7x57MT):
static inline int test_clz32(uint32_t value)
{
if (value != 0) {
return __builtin_clz(value);
} else {
return 32;
}
}
/* returns -1 if x == 0 */
int firstone(uint32_t x)
{
return 31 - test_clz32(x);
}
The result assembly:
firstone:
bsr eax, edi
ret
Note that the lzcnt instruction has a defined behavior to return the operand
size when operand is zero.
[Bug c++/100699] New: g++ doesn't warn uninitialized field when the class is derived from another class
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100699
Bug ID: 100699
Summary: g++ doesn't warn uninitialized field when the class is
derived from another class
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
GCC doesn't warn on the following code when class B is a derived class.
--- test.hh ---
#include
class Base
{
int v;
public:
Base(int u): v(u) {}
int get() { return v; }
};
class A
{
int a;
public:
A(int a_): a(a_) {}
void print() { printf("%d\n", a); }
};
class B: public Base
{
A a;
int b;
public:
B(int b_);
void print() { a.print(); }
};
-- end of test.hh ---
- test.cpp -
#include "test.hh"
B::B(int b_):
Base(b_),
a(b), b(100)
{}
end of test.cpp ---
clang++ warns as follows:
$ clang++ -Og -g -Wall -Wextra -c test.cpp
test.cpp:5:4: warning: field 'b' is uninitialized when used here
[-Wuninitialized]
a(b), b(100)
^
1 warning generated.
[Bug target/100347] [11/12 Regression] GCC 11 does not recognize skylake; translates "march=native" to "x86_64"
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100347 Iru Cai changed: What|Removed |Added CC||mytbk920423 at gmail dot com --- Comment #6 from Iru Cai --- I've checked host_detect_local_cpu() in gcc/config/i386/driver-i386.c. GCC detects x86 host CPU micro architecture by cpuid instruction instead of the APIs provided by the OS.
[Bug c/97982] integer casting after abs() causes undefined behavior
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97982 --- Comment #1 from Iru Cai --- Hmm, I saw in the abs(3) that "Trying to take the absolute value of the most negative integer is not defined." But it's still strange to see a uint32->uint64_t cast results in a negative value.
[Bug c/97982] New: integer casting after abs() causes undefined behavior
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97982
Bug ID: 97982
Summary: integer casting after abs() causes undefined behavior
Product: gcc
Version: 10.2.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: mytbk920423 at gmail dot com
Target Milestone: ---
The following code has different result when compiling with -O0/-O1 and -O2.
Also, ubsan will report an error. But I don't know why the
signed(INT_MIN)->unsigned data conversion is undefined. It's found in GCC
10.2.0 and 4.8.5.
clang does fine with both -O0 and -O2 and reports no ubsan errors.
#include
#include
#include
int main()
{
char str[20];
scanf("%s", str);
int32_t x = strtol(str, NULL, 0);
uint32_t u = abs(x); // x=0x8000 will trigger an undefined behavior
uint64_t val = u;
printf("0x%lx\n", val);
}
