tidy: Fix potential order-of-initialization problems.

A static value in mpegtables.cpp currently depends upon a static
variable initialized in tspacket.cpp, but there is no guarantee of the
order of initialization of the object files.  Convert this value (and
a couple of others) from a "static const" to a "static constexpr" so
that the constant value can be put into the header file and avoid any
order of initialization issues.

https://clang.llvm.org/extra/clang-tidy/checks/cppcoreguidelines-interfaces-global-init.html

.clang-tidy

@@ -110,10 +110,9 @@ Checks: '-*,
         # Needs work. ,
        -cppcoreguidelines-avoid-goto,
 
+        # Good. ,
         cppcoreguidelines-init-variables,
-
-        # One instance. ,
-       -cppcoreguidelines-interfaces-global-init,
+        cppcoreguidelines-interfaces-global-init,
 
         # Tons of warnings.  Most complaining that #define should
         # become a constexpr. ,

mythtv/libs/libmythtv/mpeg/tspacket.cpp

@@ -3,15 +3,6 @@
 #include <cstdint> // for intptr_t
 #include "tspacket.h"
 
-const unsigned int TSHeader::kHeaderSize       = 4;
-
-const unsigned int TSPacket::kSize             = 188;
-const unsigned int TSPacket::kPayloadSize      = 188-4;
-
-const unsigned int TSPacket::kDVBEmissionSize  = 204;
-const unsigned int TSPacket::kISDBEmissionSize = 204;
-const unsigned int TSPacket::k8VSBEmissionSize = 208;
-
 const unsigned char TSHeader::kPayloadOnlyHeader[4] =
 {
     SYNC_BYTE,

mythtv/libs/libmythtv/mpeg/tspacket.h

@@ -152,7 +152,7 @@ class MTV_PUBLIC TSHeader
     const unsigned char* data(void) const { return m_tsData; }
     unsigned char* data(void) { return m_tsData; }
 
-    static const unsigned int kHeaderSize;
+    static constexpr unsigned int kHeaderSize {4};
     static const unsigned char kPayloadOnlyHeader[4];
   private:
     unsigned char m_tsData[4] {};
@@ -217,11 +217,11 @@ class MTV_PUBLIC TSPacket : public TSHeader
 
     QString toString(void) const;
 
-    static const unsigned int kSize;
-    static const unsigned int kPayloadSize;
-    static const unsigned int kDVBEmissionSize;
-    static const unsigned int kISDBEmissionSize;
-    static const unsigned int k8VSBEmissionSize;
+    static constexpr unsigned int kSize             {188};
+    static constexpr unsigned int kPayloadSize      {188-4};
+    static constexpr unsigned int kDVBEmissionSize  {204};
+    static constexpr unsigned int kISDBEmissionSize {204};
+    static constexpr unsigned int k8VSBEmissionSize {208};
     static const TSPacket    *kNullPacket;
   private:
     unsigned char m_tsPayload[184] {};