2.3 Compiling a Program Using the kfort Driver

The kfort command invokes a driver program that automatically calls KAP, the Fortran compiler, and the linker.

Passing default KAP qualifier settings to kfort
Because kfort calls KAP and the Fortran compiler, you can substitute the kfort command for the Fortran command. For example, to use kfort to compile myprog.f with the default KAP qualifier settings, use the command:
```
kfort myprog.f
```
The kfort command uses the KAP preprocessor on myprog.f , compiles the result with the Fortran compiler, links the object code into an executable image, and produces the following files in the current directory:
- myprog_cmp.f - The optimized source file
- myprog.out - The annotated source file showing default KAP qualifier settings
- myprog.obj - The object file
- myprog.exe - An executable file
To cause KAP to generate an executable file with a name you specify, use the /executable qualifier as follows:
```
kfort /executable=my_prog
```
my_prog.exe results.
kfort inserts /executable in front of the first file name it sees. For example, the following command line produces one executable named file_1.exe :
```
kfort /fkapargs=(/conc/ur=1) file_1.f file_2.f file_3.f
```
To see a list of the KAP qualifiers and Fortran compiler qualifiers passed by kfort , use the /verbose qualifier as follows:
```
kfort /fkapargs=(/verbose) myprog.f
```
An example of the output is as follows:
```
kapf /cmp=myprog_cmp.f myprog.f               /natural
 KAP/OpenVMS_F90   V3.2 k310801 1999031    01-Mar-1999   13:16:07
0 errors in file myprog.f

Issuing the compiler command:
 for/fast/optimize=(tune=host,level=5) myprog_cmp.f

issuing link command:
 link /EXECUTABLE=myprog.exe myprog_cmp.obj
```
Passing KAP qualifiers to kfort
The /fkapargs qualifier specifies one or more KAP command qualifiers to the preprocessor. For example, to use kfort to optimize and compile the file myprog.f using KAP qualifiers for general optimization, use the command:
```
kfort /fkapargs=(/optimize=5/roundoff=3/scalaropt=3/list=myprog_annotated.out) -
myprog.f
```
The following files result:
- myprog_cmp.f - The optimized source file
- myprog_annotated.out - The annotated source file renamed by the /list qualifier
- myprog.obj - The object file
- myprog.exe - The executable file
For descriptions of all KAP command qualifiers, see Chapter 5.
Passing Fortran compiler qualifiers to kfort
Any command-line qualifier that is valid for the Fortran compiler or the linker is valid for the kfort command. You can specify compiler qualifiers and KAP qualifiers on the same line, as follows:
```
kfort /fkapargs=(/optimize=5/roundoff=3/scalaropt=3)/nowarn  myprog.f
```
The kfort command specifies the Fortran compiler qualifiers /optimize=(tune=host,level=5) , /natural , and /fast by default. To override any of the individual compiler qualifiers encompassed by /fast , specify them on the kfort command line. For example, the following command sets the compiler qualifier /math_library=accurate and overrides the default /math_library=fast set by /fast :
```
kfort /math_library=accurate myprog.f
```
For information about the /fast compiler qualifier, see the Compaq Fortran User Manual for OpenVMS Alpha Systems.

The /optimize=(tune=host,level=5) qualifier causes the compiler to optimize to the host architecture. For example, if you want to optimize for the ev5 architecture but are compiling on an ev4 system, you should override the default setting of the /tune qualifier, as follows:

kfort  /optimize=(tune=ev4,level=4) myprog.f

The kfort command specifies the linker qualifiers /lpthread and /non_shared by default. The /non_shared qualifier causes the image to be linked with archive libraries instead of with shared libraries, often resulting in faster execution at run time. To override the /non_shared default, specify /call_shared on the command line, for example:

kfort /call_shared myprog.f

The kfort driver accepts either Fortran or Fortran 77 source input. The exception is the Fortran compiler rejects comment lines beginning with C as syntax errors. Like the fort command, the kfort command assumes by default that source files with an extension of .f90 are free format, and source files with an extension of .f , .for , or .FOR are fixed format. You can override these defaults by using a format-related qualifier with either the KAP preprocessor or with the Fortran compiler. The format-related compiler qualifiers are /free and /fixed . The corresponding KAP preprocessor qualifiers are /freeformat and /nofreeformat . Table 2-1 lists combinations of qualifiers and file extensions and the resulting assumption KAP makes about the format of the source file.

Table 2-1 kfort Assumed Source Format Based on Qualifiers and File Extensions

Qualifiers		Source File Extension
KAP	F90	.f90	.f,.for,.FOR
default	default	free	fixed
/freeformat	default	free	free
/nofreeformat	default	fixed	fixed
default	/free	free	free
default	/fixed	fixed	fixed
/freeformat	/fixed	KAP issues error message
/nofreeformat	/free	KAP issues error message

For more information about the /[no]freeformat qualifier, see Section 5.3.7. For more information about the /free and /fixed qualifiers, see the Compaq Fortran User Manual for OpenVMS Alpha Systems.

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Command-Line Qualifiers