b5eeb599__the_C___Command_Line_Compiler__Details
[Option] -P [Description] C++ compile [Details] 
Causes the compiler to compile all source files as C++ files, regardless of their extension. Use ‑P‑ to compile all .CPP files as C++ source files and all other files as C source files. The command-line option -Pext causes the compiler to compile all source files as C++ files and it changes the default extension to whatever you specify with ext. This option is provided because some programmers use different extensions as their default extension for C++ code. The option -P-ext compiles files based on their extension (.CPP compiles to C++, all other extensions compile to C) and sets the default extension (other than .CPP).
BCC32, the C++ Command-Line Compiler
Details