Macros Do Not Become Part of the Environment

• Microsoft NMAKE Utility for MS-DOS, versions 1.11, 1.12, 1.13, 1.2, 1.3, and 1.4
• Microsoft NMAKE Utility for OS/2, versions 1.11, 1.12, 1.13, and 1.21
• Microsoft NMAKE Utility for Windows NT, versions 1.4 and 1.5

SUMMARY

When NMAKE defines a macro in a makefile, it does not define a corresponding environment variable for the processes NMAKE invokes. However, if an environment variable of the same name already exists, NMAKE reassigns it to have the same value as the macro.

For example, the first sample makefile below defines a CL macro. If an environment variable named CL exists, the CL macro in the makefile temporarily reassigns the CL environment variable such that the compiler only compiles files and does not link them. If the CL environment variable does not already exist, the CL macro is not added to the environment and does not change the compiler settings.

MORE INFORMATION

To create an environment variable in a makefile, use the SET command. The second sample makefile below demonstrates creating the CL environment variable if it does not already exist in the inherited environment.

The reassignment of existing environment variables can lead to unexpected errors. In the third sample program, if the environment variable 'LINK' is defined, one of the following errors will be generated:

   LINK : error LNK1104: cannot open file "link.obj" (32 bit)

 -or-

   LINK : fatal error L1093: link.obj : object file not found (16 bit)

The following warnings for the 32 bit compiler are generated for makefiles which define the MACRO 'cl' if the environment variable 'CL' was also defined:

   Command line warning D4024 : unrecognized source file type 'cl',
        object file assumed
   Command line warning D4027 : source file 'cl' ignored

   NMK.COM and environment and macros

Sample Makefile #1

# If the CL environment variable does not exist, this makefile # compiles and links TEST.C. If the CL environment variable exists, # the makefile changes its value to "/c" and prevents the linker from # running.

CL=/c

ALL:

   cl test.c

Sample Makefile #2

# This is a modified makefile from sample 1. Because CL is set with # the SET command, the linker does not run.

INCLUDE=d:\include ALL:

   set cl=/c
   cl test.c

Sample Makefile #3

# If the LINK environment variable does not exist, this makefile # compiles and links TEST.C. If the LINK environment variable exists, # the makefile changes its value to "link" and the linker error: # LNK1104 or L1093 will be generated.

link=link

ALL:

   cl /c test.c
   $(link) test.obj