Allocating zero size memory results in implementation-defined behavior:
man:malloc(3) :
If size is 0, then malloc() returns either NULL, or a unique pointer
value that can later be successfully passed to free().
PR htop-dev/htop#70 got rid of the infrastructure for generating header
files, but it left behind some code duplication.
Some of cases are things that belong in the header file and don't need
to be repeated in the C file. Other cases are things that belong in the
C file and don't need to be in the header file.
In this commit I tried to fix all of these that I could find. When given
a choice I preferred keeping things out of the header file, unless they
were being used by someone else.
The MIN, MAX, CLAMP, MINIMUM, and MAXIMUM macros appear
throughout the codebase with many re-definitions. Make
a single copy of each in a common header file, and use
the BSD variants of MINIMUM/MAXIMUM due to conflicts in
the system <sys/param.h> headers.
Reasoning:
- implementation was unsound -- broke down when I added a fairly
basic macro definition expanding to a struct initializer in a *.c
file.
- made it way too easy (e.g. via otherwise totally innocuous git
commands) to end up with timestamps such that it always ran
MakeHeader.py but never used its output, leading to overbuild noise
when running what should be a null 'make'.
- but mostly: it's just an awkward way of dealing with C code.
Rationale (copied from htop issue #471):
The function name "setValues" is misleading. For most OOP (object-
oriented programming) contexts, setXXX functions mean they will change
some member variables of an object into something specified in
function arguments. But in the *Meter_setValues() case, the new values
are not from the arguments, but from a hard-coded source. The caller
is not supposed to change the values[] to anything it likes, but
rather to "update" the values from the source. Hence, updateValues is
a better name for this family of functions.
Removed a loop that sets the bar[] buffer with spaces and merged that
task to the snprintf() call just below. No need for the barOffset
variable. Display behavior is unchanged.
Size comparision (when compiled on Ubuntu 14.04 64-bit):
$ size htop.old htop.new
text data bss dec hex filename
137312 15112 3776 156200 26228 htop.old
137216 15112 3776 156104 261c8 htop.new
Two changes in this commit:
- All meters now explicitly specify "maxItems" property, even for just
1 item. (Exception is "container" CPU meter classes, which use
CUSTOM_METERMODE.)
- "maxItems" being 0 is now allowed. This will let bar meters and graph
meters render an empty meter.
(Cherry-picked from d56bcd8e0d8d6a177fc2e40db32fc73ea4588684, the
experimental graph coloring branch)
The variable 'dot' in GraphMeterMode_draw now means "maximum number of
dots per value (column) in graph". The old meaning was "amount of value
that is to be represented by a dot" and was always a fraction. Due to
a limitation in floating point computing, if GRAPH_HEIGHT were not a
power of 2, then rounding errors will occur on numbers like (1.0/3).
(Currently GRAPH_HEIGHT is 4 and so no precision loss.) 'dot' was used
as a divisor, and it's "division by a reciprocal". We change that to
simple multiplication.
(Cherry-picked from e93028d7fa0c5f00b5dc3336fd28abaf905cd572, the
experimental graph coloring branch)
Currently GRAPH_HEIGHT=4 . This prevents hard-coding the height of the graph
meters, and allows user to change it at compile-time.
With the CLAMP macro replacing the combination of MIN and MAX, we will
have at least two advantages:
1. It's more obvious semantically.
2. There are no more mixes of confusing uses like MIN(MAX(a,b),c) and
MAX(MIN(a,b),c) and MIN(a,MAX(b,c)) appearing everywhere. We unify
the 'clamping' with a single macro.
Note that the behavior of this CLAMP macro is different from
the combination `MAX(low,MIN(x,high))`.
* This CLAMP macro expands to two comparisons instead of three from
MAX and MIN combination. In theory, this makes the code slightly
smaller, in case that (low) or (high) or both are computed at
runtime, so that compilers cannot optimize them. (The third
comparison will matter if (low)>(high); see below.)
* CLAMP has a side effect, that if (low)>(high) it will produce weird
results. Unlike MIN & MAX which will force either (low) or (high) to
win. No assertion of ((low)<=(high)) is done in this macro, for now.
This CLAMP macro is implemented like described in glib
<http://developer.gnome.org/glib/stable/glib-Standard-Macros.html>
and does not handle weird uses like CLAMP(a++, low++, high--) .
* Use MIN() and MAX() to make sure values are inside bounds. This should
fix an issue where Meters were missing dots at the bottom.
* Remove variable 'level' and calculate on the fly.
With more dimensional arrays we have to define the array size. Use
one dimensional arrays to be more flexible.
Additionally this allows to shrink array size for ASCII.
Benny Baumann