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Pragma:
pragma ( Identifier )
pragma ( Identifier , ArgumentList )
Pragmas are a way to pass special information to the compiler and to add vendor specific extensions to D. Pragmas can be used by themselves terminated with a ‘;’, they can influence a statement, a block of statements, a declaration, or a block of declarations.
Pragmas can appear as either declarations, Pragma DeclarationBlock, or as statements, PragmaStatement.
pragma(ident); // just by itself
pragma(ident) declaration; // influence one declaration
pragma(ident): // influence subsequent declarations
declaration;
declaration;
pragma(ident) { // influence block of declarations
declaration;
declaration;
}
pragma(ident) statement; // influence one statement
pragma(ident) { // influence block of statements
statement;
statement;
}
The kind of pragma it is is determined by the Identifier. ExpressionList is a comma-separated list of AssignExpressions. The AssignExpressions must be parsable as expressions, but what they mean semantically is up to the individual pragma semantics.
Predefined Pragmas
All implementations must support these, even if by just ignoring them:
- msg
- Prints a message to the standard error stream while compiling, the
AssignExpressions must be string literals:
pragma(msg, "compiling..."); - lib
- Inserts a directive in the object file to link in the library
specified by the AssignExpression.
The AssignExpressions must be a string literal:
pragma(lib, "foo.lib");
Vendor Specific Pragmas
Vendor specific pragma Identifiers can be defined if they are prefixed by the vendor's trademarked name, in a similar manner to version identifiers:
pragma(DigitalMars_funky_extension) { ... }
Compilers must diagnose an error for unrecognized Pragmas, even if they are vendor specific ones. This implies that vendor specific pragmas should be wrapped in version statements:
version (DigitalMars)
{
pragma(DigitalMars_funky_extension)
{ ... }
}