So you think you know C?

Re:So you think you know C? by lmm on Wednesday November 09, 2016 @07:27AM (#12909690)

> eg: In a struct with member 'int a:8', The standard says that 'a' can be signed or unsigned (based on the machines default of the sign of char). But In gcc and clang, this is signed always regardless of the machine.

Wait, are you saying gcc/clang's behaviour is permitted by the standard, or not?

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Re:So you think you know C? by pksadiq on Wednesday November 09, 2016 @12:38PM (#12912483)

> Wait, are you saying gcc/clang's behaviour is permitted by the standard, or not?

It's permitted. The same way as a char can be signed or unsigned: Implementation defined. But in this case, it's always signed regardless of the architecture (against how a char is handled).

From c99 draft (n1570), J.3.9 (Implementation-defined behavior): Whether a ‘‘plain’’ int bit-field is treated as a signed int bit-field or as an unsigned int bit-field (6.7.2, 6.7.2.1).

But say, another compiler (ARM compiler) treats this differently [0]: Untill version 5 of the compiler, such an int was unsigned by default. Later versions defaulted to signed (as do gcc/clang).

[0] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc....

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