Dose "-Wall -Wextra" contain -Wconversion -Wfloat-conversion ?

[Gwen Fu via Gcc]

"gdb --args ../objdir/gcc/cc1plus -Wall -Wextra  example.cc "
When I debug to this line of code: gcc/c-family/c-warn.cc : line 1184
in function: conversion_warning:
if (!warn_conversion && !warn_sign_conversion && !warn_float_conversion )
        return false;
the program directly return false which means none of the three options
have been enabled .

However , when I execute :
"gdb --args ../objdir/gcc/cc1plus -Wall -Wextra  -Wfloat-conversion
example.cc"
Although the function"conversion_warning" doesn't return false directly ,
in the following switch statement , it was unexpectedly seen by the program
as "case COMPLEX_CST" .
but In expamle.cc , there is no complex number：
int main()
{
int a = 1/static_cast<double>(0) ;
return 0 ;
}