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diff --git a/cil/doc/cil010.html b/cil/doc/cil010.html new file mode 100644 index 0000000..e7b1e4b --- /dev/null +++ b/cil/doc/cil010.html @@ -0,0 +1,100 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN" + "http://www.w3.org/TR/REC-html40/loose.dtd"> +<HTML> +<HEAD> + + + +<META http-equiv="Content-Type" content="text/html; charset=ANSI_X3.4-1968"> +<META name="GENERATOR" content="hevea 1.08"> + +<base target="main"> +<script language="JavaScript"> +<!-- Begin +function loadTop(url) { + parent.location.href= url; +} +// --> +</script> +<LINK rel="stylesheet" type="text/css" href="cil.css"> +<TITLE> +GCC Extensions +</TITLE> +</HEAD> +<BODY > +<A HREF="cil009.html"><IMG SRC ="previous_motif.gif" ALT="Previous"></A> +<A HREF="ciltoc.html"><IMG SRC ="contents_motif.gif" ALT="Up"></A> +<A HREF="cil011.html"><IMG SRC ="next_motif.gif" ALT="Next"></A> +<HR> + +<H2 CLASS="section"><A NAME="htoc36">10</A> GCC Extensions</H2> +The CIL parser handles most of the <TT>gcc</TT> +<A HREF="javascript:loadTop('http://gcc.gnu.org/onlinedocs/gcc-3.0.2/gcc_5.html#SEC67')">extensions</A> +and compiles them to CIL. The following extensions are not handled (note that +we are able to compile a large number of programs, including the Linux kernel, +without encountering these): +<OL CLASS="enumerate" type=1><LI CLASS="li-enumerate"> +Nested function definitions. +<LI CLASS="li-enumerate">Constructing function calls. +<LI CLASS="li-enumerate">Naming an expression's type. +<LI CLASS="li-enumerate">Complex numbers +<LI CLASS="li-enumerate">Hex floats +<LI CLASS="li-enumerate">Subscripts on non-lvalue arrays. +<LI CLASS="li-enumerate">Forward function parameter declarations +</OL> +The following extensions are handled, typically by compiling them away: +<OL CLASS="enumerate" type=1><LI CLASS="li-enumerate"> +Attributes for functions, variables and types. In fact, we have a clear +specification (see Section <A HREF="cil006.html#sec-attrib">6.4</A>) of how attributes are interpreted. The +specification extends that of <TT>gcc</TT>. +<LI CLASS="li-enumerate">Old-style function definitions and prototypes. These are translated to +new-style. +<LI CLASS="li-enumerate">Locally-declared labels. As part of the translation to CIL, we generate +new labels as needed. +<LI CLASS="li-enumerate">Labels as values and computed goto. This allows a program to take the +address of a label and to manipulate it as any value and also to perform a +computed goto. We compile this by assigning each label whose address is taken +a small integer that acts as its address. Every computed <TT>goto</TT> in the body +of the function is replaced with a <TT>switch</TT> statement. If you want to invoke +the label from another function, you are on your own (the <TT>gcc</TT> +documentation says the same.) +<LI CLASS="li-enumerate">Generalized lvalues. You can write code like <TT>(a, b) += 5</TT> and it gets +translated to CIL. +<LI CLASS="li-enumerate">Conditionals with omitted operands. Things like <TT>x ? : y</TT> are +translated to CIL. +<LI CLASS="li-enumerate">Double word integers. The type <TT>long long</TT> and the <TT>LL</TT> suffix on +constants is understood. This is currently interpreted as 64-bit integers. +<LI CLASS="li-enumerate">Local arrays of variable length. These are converted to uses of +<TT>alloca</TT>, the array variable is replaced with a pointer to the allocated +array and the instances of <TT>sizeof(a)</TT> are adjusted to return the size of +the array and not the size of the pointer. +<LI CLASS="li-enumerate">Non-constant local initializers. Like all local initializers these are +compiled into assignments. +<LI CLASS="li-enumerate">Compound literals. These are also turned into assignments. +<LI CLASS="li-enumerate">Designated initializers. The CIL parser actually supports the full ISO +syntax for initializers, which is more than both <TT>gcc</TT> and <TT>MSVC</TT>. I +(George) think that this is the most complicated part of the C language and +whoever designed it should be banned from ever designing languages again. +<LI CLASS="li-enumerate">Case ranges. These are compiled into separate cases. There is no code +duplication, just a larger number of <TT>case</TT> statements. +<LI CLASS="li-enumerate">Transparent unions. This is a strange feature that allows you to define +a function whose formal argument has a (tranparent) union type, but the +argument is called as if it were the first element of the union. This is +compiled away by saying that the type of the formal argument is that of the +first field, and the first thing in the function body we copy the formal into +a union. <BR> +<BR> +<LI CLASS="li-enumerate">Inline assembly-language. The full syntax is supported and it is carried +as such in CIL.<BR> +<BR> +<LI CLASS="li-enumerate">Function names as strings. The identifiers <TT>__FUNCTION__</TT> and +<TT>__PRETTY_FUNCTION__</TT> are replaced with string literals. <BR> +<BR> +<LI CLASS="li-enumerate">Keywords <TT>typeof</TT>, <TT>alignof</TT>, <TT>inline</TT> are supported. +</OL> +<HR> +<A HREF="cil009.html"><IMG SRC ="previous_motif.gif" ALT="Previous"></A> +<A HREF="ciltoc.html"><IMG SRC ="contents_motif.gif" ALT="Up"></A> +<A HREF="cil011.html"><IMG SRC ="next_motif.gif" ALT="Next"></A> +</BODY> +</HTML> |