Replace isnan() with better comparisons (isgreater(), etc.)

The standard isnan() function is defined to never throw FP exceptions
even when the argument is a "signaling" NaN. This makes isnan() more
expensive than (x != x) expression unless the compiler flag
'-fno-signaling-nans' is given.

Introduce functions isNaN(), isNonnegative(), isPositive(),
sumPositiveValues() and compareRealNumbers(), and replace isnan() in
htop's codebase with the new functions. These functions utilize
isgreater() and isgreaterequal() comparisons, which do not throw FP
exceptions on "quiet" NaNs, which htop uses extensively.

With isnan() removed, there is no need to suppress the warning
'-Wno-c11-extensions' in FreeBSD. Remove the code from 'configure.ac'.

Signed-off-by: Kang-Che Sung <explorer09@gmail.com>

1 files changed, 7 insertions, 10 deletions

diff --git a/freebsd/FreeBSDMachine.c b/freebsd/FreeBSDMachine.c
index 26da667a..f5d228c8 100644
--- a/freebsd/FreeBSDMachine.c
+++ b/freebsd/FreeBSDMachine.c
@@ -281,24 +281,21 @@ static inline void FreeBSDMachine_scanCPU(Machine* super) {
    // propagate frequency to all cores if only supplied for CPU 0
    if (cpus > 1) {
       if (super->settings->showCPUTemperature) {
-         double maxTemp = NAN;
+         double maxTemp = -HUGE_VAL;
          for (unsigned int i = 1; i < maxcpu; i++) {
-            const double coreTemp = this->cpus[i].temperature;
-            if (isnan(coreTemp))
-               continue;
-
-            maxTemp = MAXIMUM(maxTemp, coreTemp);
+            if (isgreater(this->cpus[i].temperature, maxTemp)) {
+               maxTemp = this->cpus[i].temperature;
+               this->cpus[0].temperature = maxTemp;
+            }
          }
-
-         this->cpus[0].temperature = maxTemp;
       }
 
       if (super->settings->showCPUFrequency) {
          const double coreZeroFreq = this->cpus[1].frequency;
          double freqSum = coreZeroFreq;
-         if (!isnan(coreZeroFreq)) {
+         if (isNonnegative(coreZeroFreq)) {
             for (unsigned int i = 2; i < maxcpu; i++) {
-               if (isnan(this->cpus[i].frequency))
+               if (!isNonnegative(this->cpus[i].frequency))
                   this->cpus[i].frequency = coreZeroFreq;
 
                freqSum += this->cpus[i].frequency;