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Compiler Reference Guide

Preface Arm Compiler Tools Overview armclang Reference armclang Command-line Options Summary of armclang command-line options -C (armclang) -c (armclang) -D -E -e -fbare-metal-pie -fbracket-depth=N -fcommon, -fno-common -fdata-sections, -fno-data-sections -ffast-math, -fno-fast-math -ffixed-rN -ffp-mode -ffunction-sections, -fno-function-sections -fident, -fno-ident @file -fldm-stm, -fno-ldm-stm -fno-builtin -fno-inline-functions -flto, -fno-lto -fexceptions, -fno-exceptions -fomit-frame-pointer, -fno-omit-frame-pointer -fpic, -fno-pic -fropi, -fno-ropi -fropi-lowering, -fno-ropi-lowering -frwpi, -fno-rwpi -frwpi-lowering, -fno-rwpi-lowering -fsanitize -fshort-enums, -fno-short-enums -fshort-wchar, -fno-short-wchar -fstack-protector, -fstack-protector-all, -fstack- -fstrict-aliasing, -fno-strict-aliasing -fsysv, -fno-sysv -ftrapv -fvectorize, -fno-vectorize -fvisibility -fwrapv -g, -gdwarf-2, -gdwarf-3, -gdwarf-4 (armclang) -I -include -L -l -M, -MM -MD, -MMD -MF -MG -MP -MT -march -marm -masm -mbig-endian -mbranch-protection -mcmodel -mcmse -mcpu -mexecute-only -mfloat-abi -mfpu -mimplicit-it -mlittle-endian -mno-neg-immediates -moutline, -mno-outline -mpixolib -munaligned-access, -mno-unaligned-access -mthumb -nostdlib -nostdlibinc -o (armclang) -O (armclang) -pedantic -pedantic-errors -Rpass -S -save-temps -shared (armclang) -std --target -U -u (armclang) -v (armclang) --version (armclang) --version_number (armclang) --vsn (armclang) -W -Wl -Xlinker -x (armclang) -### Compiler-specific Keywords and Operators Compiler-specific keywords and operators __alignof__ __asm __declspec attributes __declspec(noinline) __declspec(noreturn) __declspec(nothrow) __inline __promise __unaligned Global named register variables Compiler-specific Function, Variable, and Type Att Function attributes __attribute__((always_inline)) function attribute __attribute__((cmse_nonsecure_call)) function attr __attribute__((cmse_nonsecure_entry)) function att __attribute__((const)) function attribute __attribute__((constructor(priority))) function at __attribute__((format_arg(string-index))) function __attribute__((interrupt("type"))) function attrib __attribute__((malloc)) function attribute __attribute__((naked)) function attribute __attribute__((noinline)) function attribute __attribute__((nonnull)) function attribute __attribute__((noreturn)) function attribute __attribute__((nothrow)) function attribute __attribute__((pcs("calling_convention"))) functio __attribute__((pure)) function attribute __attribute__((section("name"))) function attribut __attribute__((unused)) function attribute __attribute__((used)) function attribute __attribute__((value_in_regs)) function attribute __attribute__((visibility("visibility_type"))) fun __attribute__((weak)) function attribute __attribute__((weakref("target"))) function attrib Type attributes __attribute__((aligned)) type attribute __attribute__((packed)) type attribute __attribute__((transparent_union)) type attribute Variable attributes __attribute__((alias)) variable attribute __attribute__((aligned)) variable attribute __attribute__((deprecated)) variable attribute __attribute__((packed)) variable attribute __attribute__((section("name"))) variable attribut __attribute__((unused)) variable attribute __attribute__((used)) variable attribute __attribute__((visibility("visibility_type"))) var __attribute__((weak)) variable attribute __attribute__((weakref("target"))) variable attrib Compiler-specific Intrinsics __breakpoint intrinsic __current_pc intrinsic __current_sp intrinsic __disable_fiq intrinsic __disable_irq intrinsic __enable_fiq intrinsic __enable_irq intrinsic __force_stores intrinsic __memory_changed intrinsic __schedule_barrier intrinsic __semihost intrinsic __vfp_status intrinsic Compiler-specific Pragmas #pragma clang system_header #pragma clang diagnostic #pragma clang section #pragma once #pragma pack(...) #pragma unroll[(n)], #pragma unroll_completely #pragma weak symbol, #pragma weak symbol1 = symbol Other Compiler-specific Features ACLE support Predefined macros Inline functions Half-precision floating-point data types Half-precision floating-point number format Half-precision floating-point intrinsics Library support for _Float16 data type BFloat16 floating-point number format TT instruction intrinsics Non-secure function pointer intrinsics armclang Integrated Assembler Syntax of assembly files for integrated assembler Assembly expressions Alignment directives Data definition directives String definition directives Floating-point data definition directives Section directives Conditional assembly directives Macro directives Symbol binding directives Org directive AArch32 Target selection directives AArch64 Target selection directives Space-filling directives Type directive Integrated assembler support for the CSDB instruct armclang Inline Assembler Inline Assembly File-scope inline assembly Inline assembly statements within a function Assembly string Output and input operands Clobber list volatile Inline assembly constraint strings Constraint modifiers Constraint codes Constraint codes common to AArch32 state and AArch Constraint codes for AArch32 state Constraint codes for AArch64 state Using multiple alternative operand constraints Inline assembly template modifiers Template modifiers common to AArch32 state and AAr Template modifiers for AArch32 state Template modifiers for AArch64 state Forcing inline assembly operands into specific reg Symbol references and branches into and out of inl Duplication of labels in inline assembly statement armlink Reference fromelf Reference armar Reference armasm Legacy Assembler Reference Appendixes

#pragma clang section

B5.3 #pragma clang section

Specifies names for one or more section types. The compiler places subsequent functions, global variables, or static variables in the named section depending on the section type. The names only apply within the compilation unit.

Syntax

#pragma clang section [section_type_list]

Where:

section_type_list

specifies an optional list of section names to be used for subsequent functions, global variables, or static variables. The syntax of section_type_list is:

section_type="name"[ section_type="name"]

You can revert to the default section name by specifying an empty string, "", for name.

Valid section types are:

  • bss.
  • data.
  • rodata.
  • text.

Usage

Use #pragma clang section [section_type_list] to place functions and variables in separate named sections. You can then use the scatter-loading description file to locate these at a particular address in memory.

  • If you specify a section name with _attribute_((section("myname"))), then the attribute name has priority over any applicable section name that you specify with #pragma clang section.
  • #pragma clang section has priority over the -ffunction-section and -fdata-section command-line options.
  • Global variables, including basic types, arrays, and struct that are initialized to zero are placed in the .bss section. For example, int x = 0;.
  • armclang does not try to infer the type of section from the name. For example, assigning a section .bss.mysec does not mean it is placed in a .bss section.
  • If you specify the -ffunction-section and -fdata-section command-line options, then each global variable is in a unique section.

Example

int x1 = 5;                     // Goes in .data section (default)
int y1;                         // Goes in .bss section (default)
const int z1 = 42;              // Goes in .rodata section (default)
char *s1 = "abc1";              // s1 goes in .data section (default). String "abc1" goes in .conststring section.

#pragma clang section bss="myBSS" data="myData" rodata="myRodata"
int x2 = 5;                     // Goes in myData section.
int y2;                         // Goes in myBss section.
const int z2 = 42;              // Goes in myRodata section.
char *s2 = "abc2";              // s2 goes in myData section. String "abc2" goes in .conststring section.

#pragma clang section rodata=""   // Use default name for rodata section.
int x3 = 5;                     // Goes in myData section.
int y3;                         // Goes in myBss section.
const int z3 = 42;              // Goes in .rodata section (default).
char *s3 = "abc3";              // s3 goes in myData section. String "abc3" goes in .conststring section.

#pragma clang section text="myText"
int add1(int x)                 // Goes in myText section.
{
    return x+1;
} 
#pragma clang section bss="" data="" text="" // Use default name for bss, data, and text sections.
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