[libcamera-devel] [PATCH] libcamera: utils: Only enable utils::hex() for integer arguments

[Laurent Pinchart]

The utils::hex() function is defined as a function template that has
implementations for integer arguments only. When given a different
argument type, the compiler will not catch the issue, but linking will
fail:

src/libcamera/libcamera.so.p/camera_sensor.cpp.o: in function `libcamera::CameraSensor::validateSensorDriver()':
camera_sensor.cpp:(.text+0x1e6b): undefined reference to `libcamera::utils::_hex libcamera::utils::hex<libcamera::ControlId const*>(libcamera::ControlId const*, unsigned int)'

Move the failure to compilation time by enabling the function for
integer arguments only. This provides better diagnostics:

../../src/libcamera/camera_sensor.cpp: In member function ‘int libcamera::CameraSensor::validateSensorDriver()’:
../../src/libcamera/camera_sensor.cpp:199:77: error: no matching function for call to ‘hex(const libcamera::ControlId*&)’

Signed-off-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
---
 include/libcamera/base/utils.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/libcamera/base/utils.h b/include/libcamera/base/utils.h
index 07685045aa05..52301254c2eb 100644
--- a/include/libcamera/base/utils.h
+++ b/include/libcamera/base/utils.h
@@ -16,6 +16,7 @@
 #include <string>
 #include <string.h>
 #include <sys/time.h>
+#include <type_traits>
 #include <utility>
 #include <vector>
 
@@ -84,7 +85,8 @@ std::basic_ostream<char, std::char_traits<char>> &
 operator<<(std::basic_ostream<char, std::char_traits<char>> &stream, const _hex &h);
 #endif
 
-template<typename T>
+template<typename T,
+	 std::enable_if_t<std::is_integral<T>::value> * = nullptr>
 _hex hex(T value, unsigned int width = 0);
 
 #ifndef __DOXYGEN__
-- 
Regards,

Laurent Pinchart