similarity index 92%
rename from CODING_STYLE
rename to CODING_STYLE.md
@@ -4,7 +4,7 @@ QEMU Coding Style
Please use the script checkpatch.pl in the scripts directory to check
patches before submitting.
-1. Whitespace
+## Whitespace
Of course, the most important aspect in any coding style is whitespace.
Crusty old coders who have trouble spotting the glasses on their noses
@@ -29,7 +29,7 @@ Spaces of course are superior to tabs because:
Do not leave whitespace dangling off the ends of lines.
-1.1 Multiline Indent
+### Multiline Indent
There are several places where indent is necessary:
@@ -53,9 +53,8 @@ For example:
In case of function, there are several variants:
- * 4 spaces indent from the beginning
- * align the secondary lines just after the opening parenthesis of the
- first
+ * 4 spaces indent from the beginning
+ * align the secondary lines just after the opening parenthesis of the first
For example:
@@ -68,7 +67,7 @@ For example:
do_something(x, do_another(y,
z));
-2. Line width
+## Line width
Lines should be 80 characters; try not to make them longer.
@@ -77,6 +76,7 @@ that use long function or symbol names. Even in that case, do not make
lines much longer than 80 characters.
Rationale:
+
- Some people like to tile their 24" screens with a 6x4 matrix of 80x24
xterms and use vi in all of them. The best way to punish them is to
let them keep doing it.
@@ -86,7 +86,7 @@ Rationale:
at all that white space on the left!") moot.
- It is the QEMU coding style.
-3. Naming
+## Naming
Variables are lower_case_with_underscores; easy to type and read. Structured
type names are in CamelCase; harder to type but standing out. Enum type
@@ -98,7 +98,7 @@ and is therefore likely to be changed.
When wrapping standard library functions, use the prefix qemu_ to alert
readers that they are seeing a wrapped version; otherwise avoid this prefix.
-4. Block structure
+## Block structure
Every indented statement is braced; even if the block contains just one
statement. The opening brace is on the line that contains the control
@@ -130,7 +130,7 @@ Rationale: a consistent (except for functions...) bracing style reduces
ambiguity and avoids needless churn when lines are added or removed.
Furthermore, it is the QEMU coding style.
-5. Declarations
+## Declarations
Mixed declarations (interleaving statements and declarations within
blocks) are generally not allowed; declarations should be at the beginning
@@ -142,7 +142,7 @@ be placed at the top of the block even if there are statements above.
On the other hand, however, it's often best to move that #ifdef/#ifndef
block to a separate function altogether.
-6. Conditional statements
+## Conditional statements
When comparing a variable for (in)equality with a constant, list the
constant on the right, as in:
@@ -156,7 +156,7 @@ Rationale: Yoda conditions (as in 'if (1 == a)') are awkward to read.
Besides, good compilers already warn users when '==' is mis-typed as '=',
even when the constant is on the right.
-7. Comment style
+## Comment style
We use traditional C-style /* */ comments and avoid // comments.
@@ -165,10 +165,12 @@ consistency of style. The checkpatch script will warn you about this.
Multiline comment blocks should have a row of stars on the left,
and the initial /* and terminating */ both on their own lines:
+
/*
* like
* this
*/
+
This is the same format required by the Linux kernel coding style.
(Some of the existing comments in the codebase use the GNU Coding
@@ -180,24 +182,24 @@ comment anyway.)
Rationale: Consistency, and ease of visually picking out a multiline
comment from the surrounding code.
-8. trace-events style
+## trace-events style
-8.1 0x prefix
+### 0x prefix
In trace-events files, use a '0x' prefix to specify hex numbers, as in:
-some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
+ some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
An exception is made for groups of numbers that are hexadecimal by
convention and separated by the symbols '.', '/', ':', or ' ' (such as
PCI bus id):
-another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
+ another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
However, you can use '0x' for such groups if you want. Anyway, be sure that
it is obvious that numbers are in hex, ex.:
-data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
+ data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
Rationale: hex numbers are hard to read in logs when there is no 0x prefix,
especially when (occasionally) the representation doesn't contain any letters
@@ -205,12 +207,13 @@ and especially in one line with other decimal numbers. Number groups are allowed
to not use '0x' because for some things notations like %x.%x.%x are used not
only in Qemu. Also dumping raw data bytes with '0x' is less readable.
-8.2 '#' printf flag
+### '#' printf flag
Do not use printf flag '#', like '%#x'.
Rationale: there are two ways to add a '0x' prefix to printed number: '0x%...'
and '%#...'. For consistency the only one way should be used. Arguments for
'0x%' are:
+
- it is more popular
- '%#' omits the 0x for the value 0 which makes output inconsistent
similarity index 88%
rename from HACKING
rename to HACKING.md
@@ -1,19 +1,22 @@
-1. Preprocessor
+QEMU Hacking
+============
-1.1. Variadic macros
+## Preprocessor
+
+### Variadic macros
For variadic macros, stick with this C99-like syntax:
-#define DPRINTF(fmt, ...) \
- do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
+ #define DPRINTF(fmt, ...) \
+ do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
-1.2. Include directives
+### Include directives
Order include directives as follows:
-#include "qemu/osdep.h" /* Always first... */
-#include <...> /* then system headers... */
-#include "..." /* and finally QEMU headers. */
+ #include "qemu/osdep.h" /* Always first... */
+ #include <...> /* then system headers... */
+ #include "..." /* and finally QEMU headers. */
The "qemu/osdep.h" header contains preprocessor macros that affect the behavior
of core system headers like <stdint.h>. It must be the first include so that
@@ -23,12 +26,12 @@ that QEMU depends on.
Do not include "qemu/osdep.h" from header files since the .c file will have
already included it.
-2. C types
+## C types
It should be common sense to use the right type, but we have collected
a few useful guidelines here.
-2.1. Scalars
+### Scalars
If you're using "int" or "long", odds are good that there's a better type.
If a variable is counting something, it should be declared with an
@@ -89,7 +92,7 @@ Finally, while using descriptive types is important, be careful not to
go overboard. If whatever you're doing causes warnings, or requires
casts, then reconsider or ask for help.
-2.2. Pointers
+### Pointers
Ensure that all of your pointers are "const-correct".
Unless a pointer is used to modify the pointed-to storage,
@@ -99,7 +102,7 @@ importantly, if we're diligent about this, when you see a non-const
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
Typedefs are used to eliminate the redundant 'struct' keyword, since type
names have a different style than other identifiers ("CamelCase" versus
@@ -114,11 +117,11 @@ 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
+### Reserved namespaces in C and POSIX
Underscore capital, double underscore, and underscore 't' suffixes should be
avoided.
-3. Low level memory management
+## Low level memory management
Use of the malloc/free/realloc/calloc/valloc/memalign/posix_memalign
APIs is not allowed in the QEMU codebase. Instead of these routines,
@@ -133,16 +136,15 @@ 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.
+ * It catches multiplication overflowing size_t;
+ * 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.
-4. String manipulation
+## String manipulation
Do not use the strncpy function. As mentioned in the man page, it does *not*
guarantee a NULL-terminated buffer, which makes it extremely dangerous to use.
@@ -151,15 +153,17 @@ use this similar function when possible, but note its different signature:
void pstrcpy(char *dest, int dest_buf_size, const char *src)
Don't use strcat because it can't check for buffer overflows, but:
-char *pstrcat(char *buf, int buf_size, const char *s)
+
+ char *pstrcat(char *buf, int buf_size, const char *s)
The same limitation exists with sprintf and vsprintf, so use snprintf and
vsnprintf.
QEMU provides other useful string functions:
-int strstart(const char *str, const char *val, const char **ptr)
-int stristart(const char *str, const char *val, const char **ptr)
-int qemu_strnlen(const char *s, int max_len)
+
+ int strstart(const char *str, const char *val, const char **ptr)
+ int stristart(const char *str, const char *val, const char **ptr)
+ int qemu_strnlen(const char *s, int max_len)
There are also replacement character processing macros for isxyz and toxyz,
so instead of e.g. isalnum you should use qemu_isalnum.
@@ -167,7 +171,7 @@ so instead of e.g. isalnum you should use qemu_isalnum.
Because of the memory management rules, you must use g_strdup/g_strndup
instead of plain strdup/strndup.
-5. Printf-style functions
+## Printf-style functions
Whenever you add a new printf-style function, i.e., one with a format
string argument and following "..." in its prototype, be sure to use
@@ -177,12 +181,13 @@ This makes it so gcc's -Wformat and -Wformat-security options can do
their jobs and cross-check format strings with the number and types
of arguments.
-6. C standard, implementation defined and undefined behaviors
+## C standard, implementation defined and undefined behaviors
C code in QEMU should be written to the C99 language specification. A copy
of the final version of the C99 standard with corrigenda TC1, TC2, and TC3
included, formatted as a draft, can be downloaded from:
- http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf
+
+ http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf
The C language specification defines regions of undefined behavior and
implementation defined behavior (to give compiler authors enough leeway to
@@ -193,17 +198,18 @@ argument...) However there are a few areas where we allow ourselves to
assume certain behaviors because in practice all the platforms we care about
behave in the same way and writing strictly conformant code would be
painful. These are:
- * you may assume that integers are 2s complement representation
- * you may assume that right shift of a signed integer duplicates
+
+ - you may assume that integers are 2s complement representation
+ - you may assume that right shift of a signed integer duplicates
the sign bit (ie it is an arithmetic shift, not a logical shift)
In addition, QEMU assumes that the compiler does not use the latitude
given in C99 and C11 to treat aspects of signed '<<' as undefined, as
documented in the GNU Compiler Collection manual starting at version 4.0.
-7. Error handling and reporting
+## Error handling and reporting
-7.1 Reporting errors to the human user
+### Reporting errors to the human user
Do not use printf(), fprintf() or monitor_printf(). Instead, use
error_report() or error_vreport() from error-report.h. This ensures the
@@ -217,7 +223,7 @@ like command line parsing, the current location is tracked
automatically. To manipulate it manually, use the loc_*() from
error-report.h.
-7.2 Propagating errors
+### Propagating errors
An error can't always be reported to the user right where it's detected,
but often needs to be propagated up the call chain to a place that can
@@ -242,7 +248,7 @@ Do not report an error to the user when you're also returning an error
for somebody else to handle. Leave the reporting to the place that
consumes the error returned.
-7.3 Handling errors
+### Handling errors
Calling exit() is fine when handling configuration errors during
startup. It's problematic during normal operation. In particular,
@@ -60,7 +60,7 @@ When submitting patches, one common approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
-guidelines set out in the HACKING and CODING_STYLE files.
+guidelines set out in the HACKING.md and CODING_STYLE.md files.
Additional information on submitting patches can be found online via
the QEMU website
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com> --- CODING_STYLE => CODING_STYLE.md | 37 +++++++++--------- HACKING => HACKING.md | 68 ++++++++++++++++++--------------- README | 2 +- 3 files changed, 58 insertions(+), 49 deletions(-) rename CODING_STYLE => CODING_STYLE.md (92%) rename HACKING => HACKING.md (88%)