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[PULL,32/36] HACKING: Document 'struct' keyword usage

Message ID 1566284395-30287-33-git-send-email-pbonzini@redhat.com
State New
Headers show
Series [PULL,01/36] kvm: i386: halt poll control MSR support | expand

Commit Message

Paolo Bonzini Aug. 20, 2019, 6:59 a.m. UTC 
From: Eduardo Habkost <ehabkost@redhat.com>

Sometimes we use the 'struct' keyword in headers to help us
reduce dependencies between header files.  Document that
practice.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 HACKING | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)
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Patch

diff --git a/HACKING b/HACKING
index 0fc3e0f..097d482 100644
--- 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