Don't include TMathBase.h in TString.h

The TString header only uses `TMath` functions that are readily
available in the standard library.

The `TMathBase.h` header is quite big, and avoiding to include it
reduces the overall cold-ccache compile time of the full ROOT project
with all default features by about 2 % on my machine, namely from 870 s
to 855 s on average.

In the places where the `TMath` functions were used but only indirectly
included via `TString.h` inclusion, the commit suggests to use the
`<cmath>` functions instead.

Author: guitargeek

README/ReleaseNotes/v638/index.md

@@ -95,6 +95,13 @@ the deprecation period was extended.
 ## JavaScript ROOT
 - A new configuration option `Jupyter.JSRoot` was added in .rootrc to set the default mode for JSROOT in Jupyter notebooks (on or off).
 
+### Optimization of ROOT header files
+
+More unused includes were removed from ROOT header files.
+For instance, `#include "TMathBase.h"` was removed from `TString.h`.
+This change may cause errors during compilation of ROOT-based code. To fix it, provide missing the includes
+where they are really required.
+This improves compile times and reduces code inter-dependency; see https://github.com/include-what-you-use/include-what-you-use/blob/master/docs/WhyIWYU.md for a good overview of the motivation.
 
 ## Versions of built-in packages
 

core/base/inc/TString.h

@@ -25,7 +25,6 @@
 
 #include "Rtypes.h"
 
-#include "TMathBase.h"
 #include <string_view>
 #include "ROOT/TypeTraits.hxx"
 #include "snprintf.h"
@@ -579,7 +578,7 @@ inline TString &TString::Append(const TString &s)
 { return Replace(Length(), 0, s.Data(), s.Length()); }
 
 inline TString &TString::Append(const TString &s, Ssiz_t n)
-{ return Replace(Length(), 0, s.Data(), TMath::Min(n, s.Length())); }
+{ return Replace(Length(), 0, s.Data(), std::min(n, s.Length())); }
 
 inline TString &TString::operator+=(const char *cs)
 { return Append(cs, cs ? (Ssiz_t)strlen(cs) : 0); }
@@ -668,7 +667,7 @@ inline TString &TString::Insert(Ssiz_t pos, const TString &s)
 { return Replace(pos, 0, s.Data(), s.Length()); }
 
 inline TString &TString::Insert(Ssiz_t pos, const TString &s, Ssiz_t n)
-{ return Replace(pos, 0, s.Data(), TMath::Min(n, s.Length())); }
+{ return Replace(pos, 0, s.Data(), std::min(n, s.Length())); }
 
 inline TString &TString::Prepend(const char *cs)
 { return Replace(0, 0, cs, cs ? (Ssiz_t)strlen(cs) : 0); }
@@ -680,16 +679,16 @@ inline TString &TString::Prepend(const TString &s)
 { return Replace(0, 0, s.Data(), s.Length()); }
 
 inline TString &TString::Prepend(const TString &s, Ssiz_t n)
-{ return Replace(0, 0, s.Data(), TMath::Min(n, s.Length())); }
+{ return Replace(0, 0, s.Data(), std::min(n, s.Length())); }
 
 inline TString &TString::Remove(Ssiz_t pos)
-{ return Replace(pos, TMath::Max(0, Length()-pos), nullptr, 0); }
+{ return Replace(pos, std::max(0, Length()-pos), nullptr, 0); }
 
 inline TString &TString::Remove(Ssiz_t pos, Ssiz_t n)
 { return Replace(pos, n, nullptr, 0); }
 
 inline TString &TString::Chop()
-{ return Remove(TMath::Max(0, Length()-1)); }
+{ return Remove(std::max(0, Length()-1)); }
 
 inline TString &TString::Replace(Ssiz_t pos, Ssiz_t n, const char *cs)
 { return Replace(pos, n, cs, cs ? (Ssiz_t)strlen(cs) : 0); }
@@ -699,7 +698,7 @@ inline TString &TString::Replace(Ssiz_t pos, Ssiz_t n, const TString& s)
 
 inline TString &TString::Replace(Ssiz_t pos, Ssiz_t n1, const TString &s,
                                  Ssiz_t n2)
-{ return Replace(pos, n1, s.Data(), TMath::Min(s.Length(), n2)); }
+{ return Replace(pos, n1, s.Data(), std::min(s.Length(), n2)); }
 
 inline TString &TString::ReplaceAll(const TString &s1, const TString &s2)
 { return ReplaceAll(s1.Data(), s1.Length(), s2.Data(), s2.Length()) ; }

core/base/inc/TStyle.h

@@ -305,7 +305,7 @@ class TStyle : public TNamed, public TAttLine, public TAttFill, public TAttMarke
    void             SetFitFormat(const char *format="5.4g") {fFitFormat = format;}
    void             SetHeaderPS(const char *header);
    void             SetHatchesLineWidth(Int_t l) {fHatchesLineWidth = l;}
-   void             SetHatchesSpacing(Double_t h) {fHatchesSpacing = TMath::Max(0.1,h);}
+   void             SetHatchesSpacing(Double_t h) {fHatchesSpacing = std::max(0.1,h);}
    void             SetTitlePS(const char *pstitle);
    void             SetJoinLinePS(Int_t joinline=0) {fJoinLinePS=joinline;} ///< Set the line join method used for PostScript, PDF and SVG output. See `TPostScript::SetLineJoin` for details.
    void             SetCapLinePS(Int_t capline=0) {fCapLinePS=capline;}     ///< Set the line cap method used for PostScript, PDF and SVG output. See `TPostScript::SetLineCap` for details.

core/base/src/TAttLine.cxx

@@ -235,7 +235,7 @@ Int_t TAttLine::DistancetoLine(Int_t px, Int_t py, Double_t xp1, Double_t yp1, D
    if (c <= 0)  return 9999;
    Double_t v     = sqrt(c);
    Double_t u     = (a - b + c)/(2*v);
-   Double_t d     = TMath::Abs(a - u*u);
+   Double_t d     = std::abs(a - u*u);
    if (d < 0)   return 9999;
 
    return Int_t(sqrt(d) - 0.5*Double_t(fLineWidth));
@@ -247,7 +247,7 @@ Int_t TAttLine::DistancetoLine(Int_t px, Int_t py, Double_t xp1, Double_t yp1, D
 void TAttLine::Modify()
 {
    if (!gPad) return;
-   Int_t lineWidth = TMath::Abs(fLineWidth%100);
+   Int_t lineWidth = std::abs(fLineWidth%100);
    if (!gPad->IsBatch()) {
       gVirtualX->SetLineColor(fLineColor);
       if (fLineStyle > 0 && fLineStyle < 30) gVirtualX->SetLineStyle(fLineStyle);

core/base/src/TAttText.cxx

@@ -312,10 +312,10 @@ Float_t TAttText::GetTextSizePercent(Float_t size)
 {
    Float_t rsize = size;
    if (fTextFont%10 > 2 && gPad) {
-      UInt_t w = TMath::Abs(gPad->XtoAbsPixel(gPad->GetX2()) -
-                            gPad->XtoAbsPixel(gPad->GetX1()));
-      UInt_t h = TMath::Abs(gPad->YtoAbsPixel(gPad->GetY2()) -
-                            gPad->YtoAbsPixel(gPad->GetY1()));
+      UInt_t w = std::abs(gPad->XtoAbsPixel(gPad->GetX2()) -
+                          gPad->XtoAbsPixel(gPad->GetX1()));
+      UInt_t h = std::abs(gPad->YtoAbsPixel(gPad->GetY2()) -
+                          gPad->YtoAbsPixel(gPad->GetY1()));
       if (w < h)
          rsize = rsize/w;
       else

core/base/src/TDirectory.cxx

@@ -29,6 +29,9 @@
 
 #include "TSpinLockGuard.h"
 
+#include <algorithm>
+#include <limits>
+
 Bool_t TDirectory::fgAddDirectory = kTRUE;
 
 const Int_t  kMaxLen = 2048;

core/base/src/TObject.cxx

@@ -47,6 +47,7 @@ class hierarchies (watch out for overlaps).
 #include <fstream>
 #include <iostream>
 #include <iomanip>
+#include <limits>
 
 #include "Varargs.h"
 #include "snprintf.h"

core/base/src/TStorage.cxx

@@ -98,7 +98,7 @@ void *ROOT::Internal::gMmallocDesc = nullptr; //is used and set in TMapFile
 
 void TStorage::EnterStat(size_t size, void *p)
 {
-   TStorage::SetMaxBlockSize(TMath::Max(TStorage::GetMaxBlockSize(), size));
+   TStorage::SetMaxBlockSize(std::max(TStorage::GetMaxBlockSize(), size));
 
    if (!gMemStatistics) return;
 

core/base/src/TString.cxx

@@ -1033,7 +1033,7 @@ TString &TString::Replace(Ssiz_t pos, Ssiz_t n1, const char *cs, Ssiz_t n2)
       return *this;
    }
 
-   n1 = TMath::Min(n1, len - pos);
+   n1 = std::min(n1, len - pos);
    if (!cs) n2 = 0;
 
    Long64_t tot = static_cast<Long64_t>(len) - n1 + n2;  // Final string length, use 64-bit long instead of 32-bit int to check for overflows
@@ -1225,7 +1225,7 @@ Ssiz_t TString::AdjustCapacity(Ssiz_t oldCap, Ssiz_t newCap)
             newCap, ms);
    }
    Ssiz_t cap = oldCap < ms / 2 - kAlignment ?
-                Recommend(TMath::Max(newCap, 2 * oldCap)) : ms - 1;
+                Recommend(std::max(newCap, 2 * oldCap)) : ms - 1;
    return cap;
 }
 
@@ -2101,7 +2101,7 @@ TString TString::Itoa(Int_t value, Int_t base)
    Int_t quotient = value;
    // Translating number to string with base:
    do {
-      buf += "0123456789abcdefghijklmnopqrstuvwxyz"[ TMath::Abs(quotient % base) ];
+      buf += "0123456789abcdefghijklmnopqrstuvwxyz"[ std::abs(quotient % base) ];
       quotient /= base;
    } while (quotient);
    // Append the negative sign
@@ -2153,7 +2153,7 @@ TString TString::LLtoa(Long64_t value, Int_t base)
    Long64_t quotient = value;
    // Translating number to string with base:
    do {
-      buf += "0123456789abcdefghijklmnopqrstuvwxyz"[ TMath::Abs(quotient % base) ];
+      buf += "0123456789abcdefghijklmnopqrstuvwxyz"[ std::abs(quotient % base) ];
       quotient /= base;
    } while (quotient);
    // Append the negative sign

core/base/src/TTimeStamp.cxx

@@ -49,6 +49,8 @@ NOTE: the use of time_t (and its default implementation as a 32 int)
 #endif
 #include "TVirtualMutex.h"
 
+#include <cmath>
+
 ClassImp(TTimeStamp);