void str_buf_append(const char&);

extern char byvalue( char );
extern char byref( const char & );
int main( int argc, char * argv[] )
{
    char c = byvalue( argv[0][0] ) + byref( argv[0][1] );
    return c;
}

$ g++ -O3 param.cpp -c -o param.o
$ objdump -D param.o|less

0000000000000000 <main>:
   0:   55                      push   %rbp
   1:   53                      push   %rbx
   2:   48 89 f3                mov    %rsi,%rbx
   5:   48 83 ec 08             sub    $0x8,%rsp
   9:   48 8b 06                mov    (%rsi),%rax
   c:   0f be 38                movsbl (%rax),%edi     ; %edi is character
   f:   e8 00 00 00 00          callq  14 <main+0x14>  ; byvalue
  14:   48 8b 3b                mov    (%rbx),%rdi
  17:   89 c5                   mov    %eax,%ebp
  19:   48 83 c7 01             add    $0x1,%rdi       ; %rdi is address of character
  1d:   e8 00 00 00 00          callq  22 <main+0x22>  ; byref
  22:   48 83 c4 08             add    $0x8,%rsp
  26:   01 e8                   add    %ebp,%eax
  28:   5b                      pop    %rbx
  29:   0f be c0                movsbl %al,%eax
  2c:   5d                      pop    %rbp
  2d:   c3                      retq

c:   0f be 38                movsbl (%rax),%edi     ; %edi is character
   f:   e8 00 00 00 00          callq  14 <main+0x14>  ; byvalue

19:   48 83 c7 01             add    $0x1,%rdi       ; %rdi is address of character
  1d:   e8 00 00 00 00          callq  22 <main+0x22>  ; byref

void fun (char const & c) {use (c);}
...
fun (x);
[next line]

void fun (char const c) {use (c);}
...
fun (x);
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