2.2. Common compilation flags

Usual flags like -O, -O1, -O2, -O3, -D, -c, -o, … are recognized by Mercurium.

Almost every Mercurium-specific flag is of the form --xxx.

Mercurium drivers are deliberately compatible with gcc. This means that flags of the form -fXXX, -mXXX and -Wxxx are accepted and passed onto the backend compiler without interpretation by Mercurium drivers.

Warning

In GCC a flag of the form -fXXX is equivalent to a flag of the form --XXX. This is not the case in Mercurium.

2.2.1. Getting command line help

You can get a summary of all the flags accepted by Mercurium using --help with any of the drivers:

$ mcc --help
Usage: mcc options file [file..]
Options:
  -h, --help               Shows this help and quits
  --version                Shows version and quits
  --v, --verbose           Runs verbosely, displaying the programs
                           invoked by the compiler
...

2.2.2. Passing vendor-specific flags

While almost every gcc of the form -fXXX or -mXXX can be passed directly to a Mercurium driver, some other vendor-specific flags may not be well known or be misunderstood by Mercurium. When this happens, Mercurium has a generic way to pass parameters to the backend compiler and linker.

--Wn,<comma-separated-list-of-flags>
Passes comma-separated flags to the native compiler. These flags are used when Mercurium invokes the backend compiler to generate the object file (.o)
--Wl,<comma-separated-list-of-flags>
Passes comma-separated-flags to the linker. These flags are used when Mercurium invokes the linker
--Wp,<comma-separated-list-of-flags>
Passes comma-separated flags to the C/Fortran preprocessor. These flags are used when Mercurium invokes the preprocessor on a C or Fortran file.

These flags can be combined. Flags --Wp,a --Wp,b are equivalent to --Wp,a,b. Flag --Wnp,a is equivalent to --Wn,a --Wp,a

Important

Do not confuse --Wl and --Wp with the gcc similar flags -Wl and -Wp (note that gcc ones have a single -). The latter can be used with the former, as in --Wl,-Wl,muldefs. That said, Mercurium supports -Wl and -Wp directly, so -Wl,muldefs should be enough.