format string argument type does not respect C++-style cast

[Paul Cornett]

void f(int x)
{
    printf("%u", (unsigned)x);
    printf("%u", unsigned(x));
}

cppcheck --enable=warning --language=c++ t.cpp

elicits

[t.cpp:4]: (warning) %u in format string (no. 1) requires 'unsigned int' but the argument type is 'int'

for line 4 but not for line 3.

[versat]

It really seems like Cppcheck does not handle these functional casts. At least in this case.

#include <cstdio>

void f(int x)
{
    printf("%u", (unsigned)x);
    printf("%u", unsigned(x));
}

$ g++ -Wall -Wextra -fsyntax-only t.cpp && ./cppcheck --enable=all --debug t.cpp
Checking t.cpp ...

##file t.cpp
3: void f ( int x@1 )
4: {
5: printf ( "%u" , ( unsigned int ) x@1 ) ;
6: printf ( "%u" , unsigned int ( x@1 ) ) ;
7: }

##Value flow
Line 5
  "%u" always "%u"
Line 6
  "%u" always "%u"
[t.cpp:6]: (warning) %u in format string (no. 1) requires 'unsigned int' but the argument type is 'int'.
[t.cpp:3]: (style) The function 'f' is never used.
(information) Cppcheck cannot find all the include files (use --check-config for details)

Even with a typedef it does not work:

#include <cstdio>
typedef unsigned int uint;

void f(int x)
{
    printf("%u", (unsigned)x);
    printf("%u", uint(x));
}

$ g++ -Wall -Wextra -fsyntax-only t.cpp && ./cppcheck --enable=all --debug t.cpp
Checking t.cpp ...

##file t.cpp
4: void f ( int x@1 )
5: {
6: printf ( "%u" , ( unsigned int ) x@1 ) ;
7: printf ( "%u" , unsigned int ( x@1 ) ) ;
8: }

##Value flow
Line 6
  "%u" always "%u"
Line 7
  "%u" always "%u"
[t.cpp:7]: (warning) %u in format string (no. 1) requires 'unsigned int' but the argument type is 'int'.
[t.cpp:4]: (style) The function 'f' is never used.
(information) Cppcheck cannot find all the include files (use --check-config for details)

[versat]

Thank you for the report.
I created ticket 8969

[Paul Cornett]

Might have something to do with unsigned expanding to unsigned int, as casting to int works as expected.

void f(unsigned x)
{
    printf("%d", int(x));
}