µVision4 User's Guide

MDK-ARM C/C++ Compiler

Preprocessor Symbols

Define

Sets preprocessor symbols which can be checked with #if, #ifdef and #ifndef. The defined names are copied exactly as they are entered (case-sensitive). Optionally, each name may get a value. Define: Check, NoExtRam, X1=1+5 is identical to the following C preprocessor #define statements:
   #define Check
   #define NoExtRam
   #define X1 1+5

Undefine

Clears previous Define assignments that are entered in the options dialog of a higher Target or Group level.

Language / Code Generation

Enable ARM/Thumb Interworking

Generates code that can be called in any CPU mode (ARM or Thumb). The option is available only for CPUs that can switch between ARM and Thumb mode. Sets the compiler command-line option --apcs=interwork.

Optimization

Control compiler code optimization for the generated code. Sets the compiler command-line option -Onum:

• Default: Use the compiler default or the setting of a higher Target or Group level.
• Level 0 (-O0): Turn off all optimization, except some simple source transformations.
• Level 1 (-O1): Turn off optimizations that seriously degrade the debug view.
• Level 2 (-O2): High optimization (default level). The debug view might be less satisfactory because the mapping of object code to source code is not always clear.
• Level 3 (-O3): Maximum optimization. Note that Level 3 in combination with Optimize for Time may generate more code that Level 2 since it may unroll loops.

Optimize for Time

Reduce execution time at the possible expense of a larger code size. Sets the compiler command-line option -Otime. If not enabled, the compiler assumes -Ospace.

Split Load and Store Multiple

Instructs the compiler to split LDM and STM instructions into two or more LDM or STM instructions to reduce interrupt latency. When the LDM/STM have more than 5 (more than 4 when the PC is changed) CPU registers, several LDM/STM instructions are generated. Sets the compiler command-line option --split_ldm.

One ELF Section per Function

Generate one ELF section for each function in source file. Output sections are named with the same name as the function that generates the section. Allows to optimize code or to locate each function on individual memory addresses. Sets the compiler command-line option --split_sections.

Strict ANSI C

Check for strict ANSI C conformance of the source file. Sets the compiler command-line option --strict.

Enum Container always int

When disabled, the data type container for enum is optimize according the value range. When enabled, the data type container for enum is always signed int. Sets the compiler command-line option --enum_is_int.

Plain Char is Signed

Instructs the Compiler to treat all variables declared with plain char as signed char variables. Sets the compiler command-line option --signed_chars.

Read-Only Position Independent

Generate position independent code for const (ROM) accesses. Sets the compiler command-line option --apcs=/ropi.

Read-Write Position Independent

Generate position independent code for variable (RAM) accesses. Sets the compiler command-line option --apcs=/rwpi.

Warnings

Control generation of warning messages. Default is unspecified, which defaults to All Warnings. The selection No Warnings sets the command-line option -W.

Thumb Mode

Select explicitly Thumb or ARM code for a file or file group. Note: in the dialog Target the selection of the field Code Generation sets the default.

No Auto Includes

Suppress all C/C++ paths that are included automatically during compilation. System includes, such as stdio.h, are not affected by the settings of this box. Compiler auto-include paths can be viewed in the field Compiler control string.

Include Paths

Allows you to supply one or more (separated by semi-colon) paths to search for header files. For example, for #include "filename.h" the Compiler searches the current folder first and then the folder of the source file. When this fails or when #include <filename.h> is used, the paths specified in the include paths box are searched. When this search fails again, then the paths specified in the field INC under Project — Components, Environment, Books ... are used.

Misc Controls

Specify any directive for which there is no individual dialog control.

Compiler control string

Displays the current directives at the Compiler command line.