Fortunately, Microsoft’s stance on this issue has changed. MSVC++ version 12.0 (part of Visual Studio 2013) added support for _Bool type. Compound literals. Designated initializers. Mixing declarations with code. __func__ predefined identifier. You can check the _MSC_VER macro for values greater than or equal to 1800 to see whether these features are supported. Standard library … Read more
As several others have said, this is a GCC extension, not part of any standard. You’ll get a warning for it if you use the -pedantic switch. The point of this extension is not really visible in this case, but imagine if instead it was retval = foo() ?: desc.error; With the extension, foo() is … Read more
I think you’re right, it’s not possible to implement memmove efficiently in standard C. The only truly portable way to test whether the regions overlap, I think, is something like this: for (size_t l = 0; l < len; ++l) { if (src + l == dst) || (src + l == dst + len … Read more
A way to design your way around this, if needed, is to use two different types for the same object: one read/write type and one read-only type. typedef struct { char *ptrChar; } A_rw; typedef struct { const char* ptrChar; } A_ro; typedef union { A_rw rw; A_ro ro; } A; If a function needs … Read more
The key thing to remember is that const and “constant” mean two quite different things. The const keyword really means “read-only”. A constant is a numeric literal, such as 42 or 1.5 (or an enumeration or character constant). A constant expression is a particular kind of expression that can be evaluated at compile time, such … Read more
An enum is guaranteed to be represented by an integer, but the actual type (and its signedness) is implementation-dependent. You can force an enumeration to be represented by a signed type by giving one of the enumerators a negative value: enum SignedEnum { a = -1 }; In C++0x, the underlying type of an enumeration … Read more
The struct you’re returning is not an anonymous struct. The C standard defines an anonymous struct as a member of another struct that doesn’t use a tag. What you’re returning is a struct without a tag, but since it isn’t a member, it is not anonymous. GCC uses the name < anonymous > to indicate … Read more
glibc uses libnss to support a number of different providers for address resolution services. Unfortunately, you cannot statically link libnss, as exactly what providers it loads depends on the local system’s configuration.
Good overviews of C11 standard: https://en.wikipedia.org/wiki/C11_(C_standard_revision) http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf https://smartbear.com/blog/test-and-monitor/c11-a-new-c-standard-aiming-at-safer-programming/ The standard includes several changes to the C99 language and library specifications, such as: Alignment specification (_Alignas specifier, _Alignof operator, aligned_alloc function, <stdalign.h> header file) The _Noreturn function specifier and the <stdnoreturn.h> header file Type-generic expressions using the _Generic keyword. For example, the following macro cbrt(x) translates … Read more
See also What are extern variables in C. This is mentioned in the C standard in informative Annex J as a common extension: J.5.11 Multiple external definitions There may be more than one external definition for the identifier of an object, with or without the explicit use of the keyword extern; if the definitions disagree, … Read more