Fix clang 10 -Wimplicit-int-float-conversion warnings

[alexxy/gromacs.git] / src / gromacs / fileio / libxdrf.cpp

diff --git a/src/gromacs/fileio/libxdrf.cpp b/src/gromacs/fileio/libxdrf.cpp
index 3c336fda934e0e46480b762d95ccd77569a6dc1a..2099e5e798f39a2fee503ac60aef7e0222025a59 100644 (file)
--- a/src/gromacs/fileio/libxdrf.cpp
+++ b/src/gromacs/fileio/libxdrf.cpp
@@ -62,7 +62,14 @@ const char* xdr_datatype_names[] = { "int", "float", "double", "large int", "cha
  | with some routines to assist in this task (those are marked
  | static and cannot be called from user programs)
  */
-#define MAXABS (INT_MAX - 2)
+
+// Integers above 2^24 do not have unique representations in
+// 32-bit floats ie with 24 bits of precision.  We use maxAbsoluteInt
+// to check that float values can be transformed into an in-range
+// 32-bit integer. There is no need to ensure we are within the range
+// of ints with exact floating-point representations. However, we should
+// reject all floats above that which converts to an in-range 32-bit integer.
+const float maxAbsoluteInt = nextafterf(float(INT_MAX), 0.f); // NOLINT(cert-err58-cpp)
 
 #ifndef SQR
 #    define SQR(x) ((x) * (x))
@@ -490,7 +497,7 @@ int xdr3dfcoord(XDR* xdrs, float* fp, int* size, float* precision)
             {
                 lf = *lfp * *precision - 0.5;
             }
-            if (std::fabs(lf) > MAXABS)
+            if (std::fabs(lf) > maxAbsoluteInt)
             {
                 /* scaling would cause overflow */
                 errval = 0;
@@ -514,7 +521,7 @@ int xdr3dfcoord(XDR* xdrs, float* fp, int* size, float* precision)
             {
                 lf = *lfp * *precision - 0.5;
             }
-            if (std::fabs(lf) > MAXABS)
+            if (std::fabs(lf) > maxAbsoluteInt)
             {
                 /* scaling would cause overflow */
                 errval = 0;
@@ -538,7 +545,7 @@ int xdr3dfcoord(XDR* xdrs, float* fp, int* size, float* precision)
             {
                 lf = *lfp * *precision - 0.5;
             }
-            if (std::abs(lf) > MAXABS)
+            if (std::abs(lf) > maxAbsoluteInt)
             {
                 /* scaling would cause overflow */
                 errval = 0;
@@ -575,9 +582,9 @@ int xdr3dfcoord(XDR* xdrs, float* fp, int* size, float* precision)
             return 0;
         }
 
-        if (static_cast<float>(maxint[0]) - static_cast<float>(minint[0]) >= MAXABS
-            || static_cast<float>(maxint[1]) - static_cast<float>(minint[1]) >= MAXABS
-            || static_cast<float>(maxint[2]) - static_cast<float>(minint[2]) >= MAXABS)
+        if (static_cast<float>(maxint[0]) - static_cast<float>(minint[0]) >= maxAbsoluteInt
+            || static_cast<float>(maxint[1]) - static_cast<float>(minint[1]) >= maxAbsoluteInt
+            || static_cast<float>(maxint[2]) - static_cast<float>(minint[2]) >= maxAbsoluteInt)
         {
             /* turning value in unsigned by subtracting minint
              * would cause overflow