(C++) left shift count >= width of type

 

left shift count >= width of type is a compile warning when bit shifting too much up:

 

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#include <cinttypes> int main() {   const int64_t i = (1 << 63); //Gives warning }

 

The code shown, however, might give this compile warning unexpectedly. Sure, a 1 shifted 63 times up will fit in a 64-bit int. But the 1 itself must be 64 bit as well:

 

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#include <cinttypes> int main() {   const int64_t i = (1LL << 63); }

 

 

 

 

 

Technical facts

 

Application type(s)

• Desktop application

Operating system(s) or programming environment(s)

• Lubuntu 12.10 (quantal)

IDE(s):

• Qt Creator 2.5.2

Project type:

• Console application

C++ standard:

• C++11

Compiler(s):

• G++ 4.7.2

Libraries used:

• STL: GNU ISO C++ Library, version 4.7.2

 

 

 

 

 

Qt project file: CppCompileWarningLeftShiftCounterBiggerOrEqualToWidthOfType.pro

 

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TEMPLATE = app QMAKE_CXXFLAGS += -std=c++11 -Wall -Wextra -Weffc++ -Werror CONFIG += console CONFIG -= qt SOURCES += main.cpp

 

 

 

 

 

main.cpp

 

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#include <cinttypes> #include <iostream> int main() {   //const int64_t i = (1 << 63); //Gives warning   const int64_t i = (1LL << 63);   std::cout << i << '\n'; }

 

• Download the Qt Creator project 'CppCompileWarningLeftShiftCounterBiggerOrEqualToWidthOfType' (zip)