ARM Compiler toolchain v4.1 for µVision Using the Compiler

Getting started with the Compiler
3.4 Order of compiler command-line options
In general, compiler command-line options can appear in any order in a single compiler
invocation. However, the effects of some options depend on the order they appear in the
command line and how they are combined with other related options, for example, optimization
options prefixed by -O, or PreCompiled Header (PCH) options.
The compiler enables you to use multiple options even where these might conflict. This means
that you can append new options to an existing command line, for example, in a makefile or a
via file.
Where options override previous options on the same command line, the last option specified
always takes precedence. For example:
armcc -O1 -O3 -Ospace -Otime ...
is executed by the compiler as:
armcc -O3 -Otime
The environment variable ARMCCnn_CCOPT can be used to specify compiler command-line
options. Options specified on the command line take precedence over options specified in the
environment variable.
To see how the compiler has processed the command line, use the --show_cmdline option. This
shows nondefault options that the compiler used. The contents of any via files are expanded. In
the example used here, although the compiler executes armcc -O2 -Otime, the output from
--show_cmdline does not include -O2. This is because -O2 is the default optimization level, and
--show_cmdline does not show options that apply by default.
3.4.1 See also
Concepts
• PreCompiled Header (PCH) files on page 4-29.
Introducing the ARM Compiler toolchain:
• Specifying command-line options with an environment variable on page 2-24.
Reference
• Compiler command-line options listed by group on page 3-4.
Introducing the ARM Compiler toolchain:
• Toolchain environment variables on page 2-12.
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