fmt: test for fmt::runtime() & require v8.0.0 or later

NEWS.md

@@ -22,6 +22,11 @@
   being copied when very large values were present in source files, or in
   error messages when very large values were used as command-line parameters.
 
+## Build system changes
+
+* Release v8.0.0 of the `fmt` library is now required. If not found, the
+  bundled copy will be used.
+
 
 # Version 83.0 "Circle Of Friends" 2024-03-10
 

README.md

@@ -124,7 +124,7 @@ distribution instead of relying on the bundled versions.
 These libraries are:
 
 - [fmt](http://fmtlib.net/) — a small, safe and fast formatting
-  library. Version 6.1.0 or later is required.
+  library. Version 8.0.0 or later is required.
 
 - [libEBML v1.4.4](http://dl.matroska.org/downloads/libebml/) or later
   and [libMatroska v1.7.1](http://dl.matroska.org/downloads/libmatroska/)

ac/fmt.m4

@@ -15,28 +15,15 @@ AC_CACHE_CHECK([fmt],[ac_cv_fmt],[
     #include <fmt/format.h>
     #include <fmt/ostream.h>
 
-    #if !defined(FMT_VERSION) || (FMT_VERSION < 60100)
-    #error fmtlib is too old, need 6.1.0 or later
+    #if !defined(FMT_VERSION) || (FMT_VERSION < 80000)
+    #error fmtlib is too old, need 8.0.0 or later
     #endif
   ]], [[
-    fmt::format("{0:02}", fmt::to_string(4254));
+    fmt::format("{0}", fmt::to_string(4254));
+    std::string moo{"'{0}' says the cow"};
+    fmt::format(fmt::runtime(moo), "moo");
   ]])],[ac_cv_fmt=yes],[ac_cv_fmt=no])
 
-  AC_CACHE_VAL(ac_cv_fmt_v8, [
-    if test $ac_cv_fmt=yes; then
-      AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
-        #include <fmt/format.h>
-        #include <fmt/ostream.h>
-
-        #if !defined(FMT_VERSION) || (FMT_VERSION < 80000)
-        #error fmt is older than v8
-        #endif
-      ]], [[
-        fmt::format("{0:02}", fmt::to_string(4254));
-      ]])],[ac_cv_fmt_v8=yes],[ac_cv_fmt_v8=no])
-    fi
-  ])
-
   CXXFLAGS="$ac_save_CXXFLAGS"
   LIBS="$ac_save_LIBS"
 
@@ -48,10 +35,6 @@ if test x"$ac_cv_fmt" = xyes; then
 else
   AC_MSG_NOTICE([Using the internal version of fmt])
   FMT_INTERNAL=yes
-  ac_cv_fmt_v8=yes
 fi
 
-if test $ac_cv_fmt_v8 = yes; then
-  AC_DEFINE([HAVE_FMT_V8],[1],[Define if the fmt library is v8 or newer])
-fi
 AC_SUBST(FMT_INTERNAL)

src/common/common.h

@@ -33,12 +33,6 @@
 
 #include <stdint.h>
 
-#if !defined(HAVE_FMT_V8) || !HAVE_FMT_V8
-// Don't support user-defined literals in fmt as they aren't used by
-// MKVToolNix and produce a compiler warning in -Wpedantic with fmt < v8
-#  define FMT_USE_USER_DEFINED_LITERALS 0
-#endif
-
 #include <fmt/format.h>
 #include <fmt/ostream.h>