ref: 90f952cb3dee893681a64e5f08844785e6b30ea8
parent: ebf23256dfed83fa0018d4bf36b710351053af22
author: Eddie Thieda <eddie.thieda@gmail.com>
date: Thu Jan 31 17:16:57 EST 2019
Modified README file a bit.
--- a/README
+++ b/README
@@ -1,3 +1,33 @@
+Compiling
+=========
+
+SCC is a portable toolchain that can be compiled on any UNIX system
+out of the box. It supports three main configuration options that
+can be passed to the command line:
+
+ - CROSS_COMPILE:
+ Specify a prefix name for the tools called by the Makefile.
+
+ - CONF: Specify which version of libc to build.
+ Once the build process completes only the target specified in
+ CONF will be built. Supported values are:
+
+ - amd64-linux (default)
+ - amd64-darwin
+ - amd64-openbsd
+ - arm64-linux
+ - amd64-dragonfly
+ - amd64-netbsd
+ - arm32-linux
+
+ - TOOL: Specify the toolchain type to be used. Possible
+ supported values are:
+
+ - unix (by default)
+ - gnu
+ - gnu-darwin
+ - clang
+
Deviations from standard C
===========================
This compiler aims to be fully compatible with the C99 standard, but
@@ -10,7 +40,7 @@
unnecessary complexity to the compiler (and increased compilation time):
- const: The definition of const is not clear in the standard.
- If a const value is modified the behaviour is undefined
+ If a const value is modified the behavior is undefined
behaviour. It seems it was defined in order to be able to
allocate variables in ROM rather than error detection. This
implememtation will not warn about these modifications and
@@ -21,7 +51,7 @@
to be able to deal with longjmp (local variables that are not
volatile have undefined state) and for memory mapped registers
or variables whose values are modified asynchronously. This can
- be achieved with special pragma values though.
+ be achieved by using special pragma values though.
In the first case, it generates a lot of problems with modern
processors and multithreading, when not holding the value in a
register is not good enough (an explicit memory barrier is needed).
@@ -32,8 +62,8 @@
of portable programs that use longjmp, this specifier eventually
will be implemented.
- - restrict: This qualifier can only be applied to pointers to
- mark that the pointed object has no other alias. This qualifier
+ - restrict: This qualifier can only be applied to pointers that
+ mark the pointed object and has no other alias. This qualifier
was introduced to be able to fix some performance problems in
numerical algorithms, where FORTRAN could achieve a better
performance (and in fact even with this specifier FORTRAN has a
@@ -70,7 +100,7 @@
because it is understood as a parameter of function pointer type.
This complexity is not needed at all as function pointers fix all these
-problems without this complexity (and they are the more usual
+problems without this complexity (and they are the more common
way of writing such code).
- Definition of variables with incomplete type
@@ -78,9 +108,9 @@
C89 allows the definition of variables with incomplete type that
have external linkage and file scope. The type of the variable
-is the composition of all the definitions find in the file. The exact
+is the composition of all the definitions found in the file. The exact
rules are a bit complex (3.7.2) so SCC ignores them at this moment
-and it does not allow any definition of variables with incomplete type.
+by simply not allowing any definition of variables with incomplete type.
If you don't believe me try this code:
@@ -93,9 +123,9 @@
- Variadic function alike macros
------------------------------
-The standard (C99 6.10.3 c 4) forces to pass more parameters than
+The standard (C99 6.10.3 c 4) forces passing more parameters than
the number of parameters present in the variadic argument list
-(excluding ...). Scc accepts a parameter list with the same number
+(excluding ...). SCC accepts a parameter list with the same number
of arguments.
#define P(a, ...) a