target/arm: Convert T16, Conditional branches, Supervisor call

[qemu.git] / HACKING

diff --git a/HACKING b/HACKING
index 4125c97d8d177b11f0d4367d6d81224fdd2ff2ba..097d48260391039ac4ba64d20949d3040d2a0ee6 100644 (file)
--- a/HACKING
+++ b/HACKING
@@ -100,7 +100,19 @@ pointer, you're guaranteed that it is used to modify the storage
 it points to, or it is aliased to another pointer that is.
 
 2.3. Typedefs
-Typedefs are used to eliminate the redundant 'struct' keyword.
+
+Typedefs are used to eliminate the redundant 'struct' keyword, since type
+names have a different style than other identifiers ("CamelCase" versus
+"snake_case").  Each named struct type should have a CamelCase name and a
+corresponding typedef.
+
+Since certain C compilers choke on duplicated typedefs, you should avoid
+them and declare a typedef only in one header file.  For common types,
+you can use "include/qemu/typedefs.h" for example.  However, as a matter
+of convenience it is also perfectly fine to use forward struct
+definitions instead of typedefs in headers and function prototypes; this
+avoids problems with duplicated typedefs and reduces the need to include
+headers from other headers.
 
 2.4. Reserved namespaces in C and POSIX
 Underscore capital, double underscore, and underscore 't' suffixes should be
@@ -118,6 +130,15 @@ Please note that g_malloc will exit on allocation failure, so there
 is no need to test for failure (as you would have to with malloc).
 Calling g_malloc with a zero size is valid and will return NULL.
 
+Prefer g_new(T, n) instead of g_malloc(sizeof(T) * n) for the following
+reasons:
+
+  a. It catches multiplication overflowing size_t;
+  b. It returns T * instead of void *, letting compiler catch more type
+     errors.
+
+Declarations like T *v = g_malloc(sizeof(*v)) are acceptable, though.
+
 Memory allocated by qemu_memalign or qemu_blockalign must be freed with
 qemu_vfree, since breaking this will cause problems on Win32.