What s the difference between PRETTY FUNCTION FUNCTION func

Question

What s the difference between   PRETTY FUNCTION      FUNCTION      func    and where are they documented  How do I decide which one to use

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func   is documented in the C  0x standard at section 8 4 1  In this case it s a predefined  function local variable of the form   static const char   func        function-name      where  function name  is implementation specfic  This means that whenever you declare a function  the compiler will add this variable implicitly to your function  The same is true of   FUNCTION   and   PRETTY FUNCTION    Despite their uppercasing  they aren t macros  Although   func   is an addition to C  0x   g   -std c  98        will still compile code using   func       PRETTY FUNCTION   and   FUNCTION   are documented here http   gcc gnu org onlinedocs gcc-4 5 1 gcc Function-Names html Function-Names    FUNCTION   is just another name for   func      PRETTY FUNCTION   is the same as   func   in C but in C   it contains the type signature as well

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For those  who wonder how it goes in VS   MSVC 2015 Update 1  cl exe version 19 00 24215 1    include  lt iostream gt   template lt typename X  typename Y gt  struct A     template lt typename Z gt    static void f           std  cout  lt  lt   from A  f      lt  lt  std  endl        lt  lt    FUNCTION    lt  lt  std  endl        lt  lt    func    lt  lt  std  endl        lt  lt    FUNCSIG    lt  lt  std  endl          void main       std  cout  lt  lt   from main      lt  lt  std  endl      lt  lt    FUNCTION    lt  lt  std  endl      lt  lt    func    lt  lt  std  endl      lt  lt    FUNCSIG    lt  lt  std  endl  lt  lt  std  endl     A lt int  float gt   f lt bool gt         output    from main    main main int   cdecl main void   from A  f    A lt int float gt   f f void   cdecl A lt int float gt   f ltbool gt  void    Using of   PRETTY FUNCTION   triggers undeclared identifier error  as expected

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PRETTY FUNCTION   handles C   features  classes  namespaces  templates and overload main cpp  include  lt iostream gt   namespace N       class C           public              template  lt class T gt              static void f int i                     void i                  std  cout  lt  lt   quot   func               quot   lt  lt    func    lt  lt  std  endl                            lt  lt   quot   FUNCTION           quot   lt  lt    FUNCTION    lt  lt  std  endl                            lt  lt   quot   PRETTY FUNCTION    quot   lt  lt    PRETTY FUNCTION    lt  lt  std  endl                            template  lt class T gt              static void f double f                     void f                  std  cout  lt  lt   quot   PRETTY FUNCTION    quot   lt  lt    PRETTY FUNCTION    lt  lt  std  endl                          int main         N  C  f lt char gt  1       N  C  f lt void gt  1 0      Compile and run  g   -ggdb3 -O0 -std c  11 -Wall -Wextra -pedantic -o main out main cpp   main out  Output    func              f   FUNCTION          f   PRETTY FUNCTION   static void N  C  f int   with T   char    PRETTY FUNCTION   static void N  C  f double   with T   void   You may also be interested in stack traces with function names  print call stack in C or C   Tested in Ubuntu 19 04  GCC 8 3 0  C  20 std  source location  function name http   www open-std org jtc1 sc22 wg21 docs papers 2019 p1208r5 pdf went into C  20  so we have yet another way to do it  The documentation says   constexpr const char  function name   const noexcept  6 Returns  If this object represents a position in the body of a function  returns an implementation-defined NTBS that should correspond to the function name  Otherwise  returns an empty string   where NTBS means  quot Null Terminated Byte String quot   I ll give it a try when support arrives to GCC  GCC 9 1 0 with g  -9 -std c  2a still doesn t support it  https   en cppreference com w cpp utility source location claims usage will be like   include  lt iostream gt   include  lt string view gt   include  lt source location gt    void log std  string view message           const std  source location amp  location std  source location  current           std  cout  lt  lt   quot info  quot                 lt  lt  location file name    lt  lt   quot   quot                 lt  lt  location line    lt  lt   quot   quot                 lt  lt  location function name    lt  lt   quot   quot                 lt  lt  message  lt  lt    n       int main         log  quot Hello world  quot       Possible output  info main cpp 16 main Hello world   so note how this returns the caller information  and is therefore perfect for usage in logging  see also  Is there a way to get function name inside a C   function

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func   is an implicitly declared identifier that expands to a character array variable containing the function name when it is used inside of a function   It was added to C in C99   From C99   6 4 2 2 1   The identifier   func   is implicitly declared by the translator as if  immediately following the opening brace of each function definition  the declaration static const char   func        quot function-name quot    appeared  where function-name is the name of the lexically-enclosing function   This name is the unadorned name of the function   Note that it is not a macro and it has no special meaning during preprocessing    func   was added to C   in C  11  where it is specified as containing  quot an implementation-de ned string quot   C  11   8 4 1 dcl fct def general  8   which is not quite as useful as the specification in C   The original proposal to add   func   to C   was N1642     FUNCTION   is a pre-standard extension that some C compilers support  including gcc and Visual C     in general  you should use   func   where it is supported and only use   FUNCTION   if you are using a compiler that does not support it  for example  Visual C    which does not support C99 and does not yet support all of C  0x  does not provide   func       PRETTY FUNCTION   is a gcc extension that is mostly the same as   FUNCTION    except that for C   functions it contains the  quot pretty quot  name of the function including the signature of the function   Visual C   has a similar  but not quite identical  extension    FUNCSIG    For the nonstandard macros  you will want to consult your compiler s documentation   The Visual C   extensions are included in the MSDN documentation of the C   compiler s  quot Predefined Macros quot    The gcc documentation extensions are described in the gcc documentation page  quot Function Names as Strings  quot

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Despite not fully answering the original question  this is probably what most people googling this wanted to see  For GCC    cat test cpp   include  lt iostream gt   int main int argc  char   argv        std  cout  lt  lt    func    lt  lt  std  endl                lt  lt    FUNCTION    lt  lt  std  endl                lt  lt    PRETTY FUNCTION    lt  lt  std  endl      g   test cpp      a out  main main int main int  char

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