Default differences

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Arm^® Compiler Migration and Compatibility Guide

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Home > Migrating from Arm Compiler 5 to Arm Compiler 6 > Default differences

2.3 Default differences

Some compiler and assembler options are different between Arm^® Compiler 5 and Arm Compiler 6, or have different default values.

Note:

This topic includes descriptions of [COMMUNITY] features. See Support level definitions.

The following table lists these differences.

Table 2-2 Differences in defaults

Arm Compiler 5	Arm Compiler 6	Notes	Further information
`‑‑hide_all`	`‑fvisibility=hidden`	These defaults are similar but `‑fvisibility=hidden` does not affect extern declarations or symbol references. In Arm Compiler 6, symbols in the final image are hidden if the reference or the definition is hidden. Therefore the visibility of the reference alone does not determine the visibility of the symbol, as it does in Arm Compiler 5.	`‑‑hide_all` for Arm^® Compiler 5. `‑fvisibility` for Arm^® Compiler 6.
`‑‑apcs=/hardfp` or `‑‑apcs=/softfp`	`‑mfloat‑abi=softfp`	The default floating-point linkage in Arm Compiler 5 depends on the specified processor. If the processor has floating-point hardware, then Arm Compiler 5 uses hardware floating-point linkage. If the processor does not have floating-point hardware, then Arm Compiler 5 uses software floating-point linkage. In Arm Compiler 6, the default is always software floating-point linkage for AArch32 state. The `‑mfloat‑abi` option also controls the type of floating-point instructions that the compiler uses. `‑mfloat‑abi=softfp` uses hardware floating-point instructions. Use `‑mfloat‑abi=soft` to use software floating-point linkage and software library functions for floating-point operations.	`‑‑apcs` for Arm^® Compiler 5. `‑mfloat‑abi` for Arm^® Compiler 6.
`__image.axf`	`a.out`	Default name for the executable image if none of `‑o`, `‑c`, `‑E`, or `‑S` are specified on the command-line.	`‑o` for Arm^® Compiler 5. `‑o` for Arm^® Compiler 6.
`‑‑enum_is_int` is disabled by default	`‑fno‑short‑enums`	`‑‑enum_is_int` is disabled by default in Arm Compiler 5, so the smallest data type that can hold the enumerator values is used. `‑fno‑short‑enums` is the default in Arm Compiler 6, so the size of the enumeration type is at least 32 bits.	`‑‑enum_is_int` for Arm^® Compiler 5. `‑fno‑short‑enums` for Arm^® Compiler 6.
`‑O2`	`‑O0`	Arm Compiler 5 uses high optimization (`-O2`) by default. Arm Compiler 6 uses minimum optimization (`-O0`) by default.	`‑O` for Arm^® Compiler 5. `‑O` for Arm^® Compiler 6. Optimization differences.
`‑‑apcs=/nointerwork`	`‑‑apcs=/interwork`	In Arm Compiler 5, `armasm` does not specify by default that code in the input file can safely interwork between A32 and T32. In Arm Compiler 6, `armasm` specifies interworking by default for AArch32 targets that support A32 and T32 instruction sets.	`‑‑apcs` for Arm^® Compiler 5. `‑‑apcs` for Arm^® Compiler 6.
C++03	C++14	In Arm Compiler 5, the default C++ source language mode is C++03. In Arm Compiler 6, the default C++ source language mode is C++14. You can override the default source language with `‑std` in Arm Compiler 6.	`‑‑cpp` for Arm^® Compiler 5. `‑std` for Arm^® Compiler 6.
C90	C11 [COMMUNITY]	In Arm Compiler 5, the default C source language mode is C90. In Arm Compiler 6, the default C source language mode is C11 [COMMUNITY]. You can override the default source language with `‑std` in Arm Compiler 6.	`‑‑c90` for Arm^® Compiler 5. `‑std` for Arm^® Compiler 6.
`‑‑no_exceptions`	`‑fexceptions` or `‑fno‑exceptions`	In Arm Compiler 5, C++ exceptions are disabled by default (`--no_exceptions`). In Arm Compiler 6, C++ exceptions are enabled by default (`-fexceptions`) for C++ sources, or disabled by default (`-fno-exceptions`) for C sources.	`‑‑no_exceptions` for Arm^® Compiler 5. `‑fexceptions` for Arm^® Compiler 6.
`‑‑wchar16`	`‑fno‑short‑wchar`	In Arm Compiler 5, the size of `wchar_t` is 2 bytes by default (`--wchar16`). In Arm Compiler 6, the size of `wchar_t` is 4 bytes by default (`-fno-short-wchar`).	`‑‑wchar16` for Arm^® Compiler 5. `‑fno-short-wchar` for Arm^® Compiler 6.
`‑‑split_sections` is disabled by default	`‑ffunction‑sections`	In Arm Compiler 5, functions are not put into separate ELF sections by default (`--split_sections` is disabled). In Arm Compiler 6, each function is put into a separate ELF section by default (`-ffunction-sections`).	`‑‑split_sections` for Arm^® Compiler 5. `‑ffunction-sections` for Arm^® Compiler 6.

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Default differences

2.3 Default differences

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