TMS34010 C Compiler - Al Kossow's Bitsavers

Runtime Environment - Memory Model
5.1 Memory Model
5.1.1 Sections
TMS34010 C treats memory as a single linear block that is partitioned into
subblocks of code and data. Each block of memory generated by a C program
will be placed into a contiguous block in the appropriate memory space.
Note that the linker, not the compiler, defines the memory map and allocates
code and data into target memory. The compiler assumes nothing about the
types of memory that are available, about any locations that are not available
(holes), or about any locations that are reserved for I/O or control purposes.
The compiler produces relocatable code, which allows the linker to allocate
code and data into the appropriate memory spaces. Each block of code and
data could be allocated individually into memory, but this is not a general
practice (an exception to this is memory-mapped I/O, although physical memory
locations can be accessed with C pointer types).
The compiler produces three relocatable blocks of code and data; these blocks,
called sections, can be allocated into memory in a variety of ways, to conform
to a variety of system configurations. For more information about sections,
please read Section 3 (Introduction to Common Object File Format) of the
TMS34010 Assembly Language Tools User's Guide.
There are two basic types of sections:
• Initialized sections contain data or executable code.
• Uninitialized sections reserve space in memory (usually RAM). A
program can use this space at run time for creating and storing variables.
The C compiler creates two initialized sections, .text and .cinit; it creates one
uninitialized section, .bss.
• The .text section is an initialized section that contains all the executable
code as well as string literals and floating-point constants.
• The .cinit section is an initialized section that contains tables for initializing
variab,les and constants.
• The .bss section is an uninitialized section; in a C program, it serves
three purposes:
It reserves space for global and static variables. At boot time, the
C boot routines copies data out of the .cinit section (which may
be in ROM) and uses it for initializing variables in .bss.
It reserves space for the system stack and the program stack.
It reserves space for use by the dynamic memory functions (malloc,
calloc, and realloc).
Note that the assembler creates an additional section called .data; the C environment
does not use this section. The linker takes the individual sections
from different modules and combines sections with the same name to create
four output sections. The complete program is made up of the compiler's
three output sections plus the assembler's .data section. You can place these
output sections anywhere in the address space, as needed, to meet system
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