5.4 XC32 C++ Compiler Options
The following are C++ compiler feature controls displayed in the MPLAB X IDE and VS Code project property dialogs, along with their corresponding driver options. When used, these options are applied at the first (code generation) stage of the compilation process.
| Option | Description | Command Line |
|---|---|---|
| Generate run time type descriptor information | Enable generation of information about every class with virtual functions for use by the C++ runtime type identification features ('dynamic_cast' and 'typeid'). If you don't use those parts of the language, you can save some space by disabling this option. Note that exception handling uses the same information, but it will generate it as needed. The 'dynamic_cast' operator can still be used for casts that do not require runtime type information, i.e., casts to void * or to unambiguous base classes. | -f[no-]rtti |
| Enable C++ exception handling | Enable exception handling. Generates extra code needed to propagate exceptions. | -f[no-]exceptions |
| Check that the pointer returned by operator 'new' is non-null | Check that the pointer returned by operator new is non-null before attempting to modify the storage allocated. | -fcheck-new |
| Generate code to check for violation of exception specification | Generate code to check for violation of exception specifications at runtime. Using this option may increase code size in production builds. | -fenforce-eh-specs |
| Option | Description | Command Line |
|---|---|---|
Enable unaligned access | Enables (or disables) reading and writing of 16- and 32-bit values from addresses that are not 16- or 32-bit aligned. By default, unaligned access is disabled for all pre-ARMv6 and all ARMv6-M architectures and enabled for all other architectures. If unaligned access is not enabled then words in packed data structures are accessed one byte at a time. | -m[no-]unaligned-access |
| Have symbols in production build | Build for debugging in a production build image. | -g |
| Isolate each function in a section | Place each function into its own section in the output file if the target supports arbitrary sections. The name of the function or the name of the data item determines the section's name in the output file. This option is useful when combined with the linker’s --gc-sections option to remove unreferenced functions. | -ffunction-sections |
| Place data into its own section | Place each data item into its own section in the output file if the target supports arbitrary sections. The name of the function or the name of the data item determines the section's name in the output file. This option is useful when combined with the linker’s --gc-sections option to remove unreferenced variables. | -fdata-sections |
| Enable toplevel reordering | Allow reordering of top-level functions, variables, and
asm statements, such that they might not be output
in the same order in which they appear in source files. When this
feature is disabled, using the -fno-toplevel-reorder
option, unreferenced static variables will not be removed. Use this
options with optimization level 1 or greater. | -f[no-]toplevel-reorder |
| Use indirect calls | Enable full-range calls, which are typically required when calling a function in another memory region. | -mlong-calls |
| Additional Options | Add options which do not have a dedicated control widget present in the properties dialog. |
| Option | Description | Command Line |
|---|---|---|
| Optimization Level | Select an optimization level. Equivalent to
-On option, where
n is an option below:0 - Do not optimize. The compiler’s goal is to reduce the cost of compilation and to make debugging produce the expected results. 1 - Optimize. Optimizing compilation takes somewhat longer, and a lot more host memory for a large function. The compiler tries to reduce code size and execution time. 2 - Optimize even more. The compiler performs nearly all supported optimizations that do not involve a space-speed trade-off. 3 - Optimize yet more favoring speed (superset of O2). s - Optimize yet more favoring size (superset of O2). | -O0 -O1 -O2 -O3 -Os |
| Unroll loops | Check to perform the optimization of loop unrolling. This is only done for loops whose number of iterations can be determined at compile time or run time. Uncheck to not unroll loops. | -funroll-loops |
| Omit frame pointer | Check to not keep the Frame Pointer in a register for functions that don’t need one. Uncheck to keep the Frame Pointer. | -fomit-frame-pointer |
| Pre-optimization instruction scheduling | Attempts to reorder instructions to eliminate instruction
stalls. Select "Default for optimization level" for this feature to be
controlled purely by the -O level selection. | -f[no-]schedule-insns |
| Post-optimization instruction scheduling | Attempts to reorder instructions to eliminate instruction
stalls. Select "Default for optimization level" for this feature to be
controlled purely by the -O level selection. | -f[no-]schedule-insns2 |
| Use common tentative definitions | Controls the placement of global variables defined without an initializer. | -f[no-]common |
| Option | Description | Command Line |
|---|---|---|
| Preprocessor macros | Project-specific preprocessor macro defines passed via the compiler’s –D option. | -Dmacro |
| Include directories | Search these directories for project-specific include files. | |
| Make warnings into errors | Check to halt compilation based on warnings as well as errors. Uncheck to halt compilation based on errors only. | -Werror |
| Additional warnings | Check to enable all warnings. Uncheck to disable warnings. | -Wall |
| Enable Address-attribute warning | Emit a warning for all uses of the
address() attribute. This option is for
engineering-support use only. | -Waddress-attribute-use |
| Support-ansi | Check to issue all warnings demanded by strict ANSI C. Uncheck to issue all warnings. | -ansi |
| Strict-ansi (VS Code only) | Issue all the warnings demanded by strict ISO C and ISO C++; reject all programs that use forbidden extensions and some other programs that do not follow ISO C and ISO C++. | -pedantic |