[Bug c/78807] New: Loop optimization trigger bus error
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78807
Bug ID: 78807
Summary: Loop optimization trigger bus error
Product: gcc
Version: 5.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: m.gcc.gnu.org at alias dot viem.se
Target Milestone: ---
Created attachment 40331
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40331&action=edit
Test program
With GCC 5.3.0 on Solaris 11 the below program ends due to bus error on sparc.
Turning of tree-loop optimizations with either of the below avoids bus error:
-fvect-cost-model=cheap
-fno-tree-loop-distribute-patterns
-fno-tree-loop-vectorize
=== bug.c ===
/*
$ gcc -m64 -O3 -fPIC -o bug bug.c
$ ./bug
Bus Error (core dumped)
*/
inline void g(unsigned size, unsigned x[], unsigned y[])
{
unsigned i;
for (i = 0; i < size; i++)
{
x[i] |= y[i];
}
for (i = 0; i < size; i++)
{
y[i] = 0;
}
}
struct A
{
long a; // Make struct A 8 byte aligned
int b; // Make x[] not 8 byte aligned
unsigned x[6];
unsigned y[6];
};
void f(struct A* a)
{
g(6, a->x, a->y);
}
int
main()
{
struct A a;
f(&a);
return 0;
}
=== END of bug.c ===
[Bug c/78807] Loop optimization trigger bus error
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78807 --- Comment #1 from Mauritz Sundell --- Created attachment 40332 --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40332&action=edit Stack trace and program disassembly Crash is in clrx operation accessing long (8 byte) word on 4 byte address alignment but not 8 byte aligned.
[Bug target/78807] Loop optimization trigger bus error
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78807 --- Comment #3 from Mauritz Sundell --- I did not have access to a Solaris/sparc machine with GCC 6. But on Linux/sparc test program do not crash compiled with GCC 6.2.0. $ uname -a Linux xxx 4.1.12-80.el6uek.sparc64 #1 SMP Wed Nov 30 03:09:10 PST 2016 sparc64 sparc64 sparc64 GNU/Linux $ bin/gcc-6.2.0/bin/gcc -m64 -O3 -fPIC -o bug78807 bug78807.c $ ./bug78807 $
[Bug c++/117259] warning: 'j.6' may be used uninitialized [-Wmaybe-unitialized] with -fsanitize=undefined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117259 --- Comment #1 from Mauritz Sundell --- (In reply to Mauritz Sundell from comment #0) > Accessing dynamically initialized array of global member function pointer should be: Accessing dynamically initialized global array of member function pointers
[Bug c++/117259] New: warning: 'j.6' may be used uninitialized [-Wmaybe-unitialized] with -fsanitize=undefined
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117259
Bug ID: 117259
Summary: warning: 'j.6' may be used uninitialized
[-Wmaybe-unitialized] with -fsanitize=undefined
Product: gcc
Version: 11.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: m.gcc.gnu.org at alias dot viem.se
Target Milestone: ---
/*
Accessing dynamically initialized array of global member function pointer using
a non const index variable gives false and ill-formed warning if compiling with
-fsanitize=undefined (bounds) and -O1.
Warning disappears if either:
1. changing to static initialization by removing user defined B constructor
2. using const index variable (with same value)
3. using -O0
4. using no -fsanitize or something else than -fsanitize=undefined,
-fsanitize=bounds, or, -fsanitize=bounds-strict
5. using gcc 10 or older
$ gcc -fsanitize=undefined -Wmaybe-uninitialized -O1 -c bug.cpp
bug.cpp: In member function 'void A::f()':
bug.cpp:48:15: warning: 'j.6' may be used uninitialized [-Wmaybe-uninitialized]
48 | (this->*bs[j].g)(); // warning: 'j.6' may be used uninitialized
| ^
bug.cpp:48:15: note: 'j.6' was declared here
48 | (this->*bs[j].g)(); // warning: 'j.6' may be used uninitialized
| ^
gcc 11.1 up to gcc 14.2 show warning.
gcc 12.1 up to gcc 14.2 also show note.
*/
struct A {
struct B {
void (A::*g) ();
B(void (A::*func)()) : g(func) {};
};
static const B bs[1];
void f();
void h(){}
};
const A::B A::bs[1] = {{&A::h}};
void A::f() {
(this->*bs[0].g)(); // no warning
const unsigned i = 0;
(this->*bs[i].g)(); // no warning
unsigned j = 0;
(this->*bs[j].g)(); // warning: 'j.6' may be used uninitialized
}
[Bug c++/116954] New: -Wsuggest-attribute=format false positive for function template
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116954
Bug ID: 116954
Summary: -Wsuggest-attribute=format false positive for function
template
Product: gcc
Version: 13.1.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
Assignee: unassigned at gcc dot gnu.org
Reporter: m.gcc.gnu.org at alias dot viem.se
Target Milestone: ---
When defining a function template that calls a standard printf function there
will a -Wsuggest-attribute=format warning when instantiated.
One can not att attribute to function definition template.
And adding a function declaration template with attribute does not help.
/*
Demonstrate -Wsuggest-attribute=format false positive for function template.
Verified also for x86-64.gcc 13.1, 13.2, 13.3, 14.1, 14.2 on godbolt.org
(2024-10-03).
> g++ --version
g++ (Gentoo 13.3.1_p20240614 p17) 13.3.1 20240614
...
> g++ -Wmissing-format-attribute temp-format.cpp
: In instantiation of 'int fn(char (&)[N], const char*, ...) [with
long unsigned int N = 20]':
:21:12: required from here
:13:27: warning: function 'int fn(char (&)[N], const char*, ...) [with
long unsigned int N = 20]' might be a candidate for 'gnu_printf' format
attribute [-Wsuggest-attribute=format]
13 | int ret = std::vsnprintf(buf, N, fmt, ap);
| ~~^
*/
#include
#include
template
int fn(char (&buf)[N], const char fmt[], ...)
__attribute__ ((__format__ (__printf__, 2, 3)));
template int fn(char (&buf)[N], const char fmt[], ...)
// __attribute__ ((__format__ (__printf__, 2, 3))) // error: attributes are
not allowed on a function-definition
{
va_list ap;
va_start(ap, fmt);
int ret = std::vsnprintf(buf, N, fmt, ap); // warning: function âint fn(char
(&)[N], const char*, ...) [with long unsigned int N = 20]â might be a candidate
for âgnu_printfâ format attribute [-Wsuggest-attribute=format]
va_end(ap);
return ret;
}
int main()
{
char buf[20];
return fn(buf, "%d", 42);
}
