Re: gEDA-user: C question
On Mar 3, 2007, at 4:57 PM, [EMAIL PROTECTED] wrote: Thanks. I threw the question to the group because I know there's plenty of knowledgable people reading willing to answer it. Anyway, I was trying to get the compiler to generate 2 versions of an initialized array: ROM, and RAM. The processor I am using has more ROM than RAM, so placing the code into ROM makes more sense, yet I was having trouble getting access it correctly due to a routine expecting a const ptr. So, I was trying it in RAM, but not sure if the code was correct. Thanks again for the help :) You didn't say which compiler you're using, nor which architecture. But Keil's 8051 compiler has the code keyword, which tells the compiler that the variable should be put into CODE space, which is by definition ROM. -a ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: C question
On Sun, 4 Mar 2007 13:58:45 -0700 Andy Peters [EMAIL PROTECTED] wrote: On Mar 3, 2007, at 4:57 PM, [EMAIL PROTECTED] wrote: Thanks. I threw the question to the group because I know there's plenty of knowledgable people reading willing to answer it. Anyway, I was trying to get the compiler to generate 2 versions of an initialized array: ROM, and RAM. The processor I am using has more ROM than RAM, so placing the code into ROM makes more sense, yet I was having trouble getting access it correctly due to a routine expecting a const ptr. So, I was trying it in RAM, but not sure if the code was correct. Thanks again for the help :) You didn't say which compiler you're using, nor which architecture. But Keil's 8051 compiler has the code keyword, which tells the compiler that the variable should be put into CODE space, which is by definition ROM. For gcc ports this keyword would be: __attribute__((section (YOURSECTION))) where YOURSECTION must be replaced with .text for code in ROM. GCC ports are not consistent though. If I develop for ARM and declare avariable as const it will end up in RAM also unless I add the __attribute__... keyword. However the MSP430 port places the variable in ROM if I only declare it as const... Maybe the reason for this behaviour is the difference in complexity in ARM and MSP430 micros... HTH, Hans -a ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user -- $ cat .sig /dev/null ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: C question
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 John Coppens schrieb: 'Static' is normally reserved to specify the data should never be destroyed by the compiler if the compiler thinks it's not necessary any more (eg. to make data 'static', i.e. available between function calls to the same function). static has two meanings: The one you mentioned for variables declared inside a function, the one Ben Jackson mentioned for variables declared outside a function. Philipp -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.6 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFF6WqKbtUV+xsoLpoRAlogAKDVJ2bMN+DsjRv63K91OjTySimyvwCg1ntE YZtmuDvJm+dFdBlZ0ugvwQo= =U2uw -END PGP SIGNATURE- ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: C question
On Sat, 03 Mar 2007 13:31:06 +0100 Philipp Klaus Krause [EMAIL PROTECTED] wrote: static has two meanings: The one you mentioned for variables declared inside a function, the one Ben Jackson mentioned for variables declared outside a function. Isn't internet great? Collaborative learning! Thanks Philipp - I had never used 'static' in Ben's way. John ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: C question
John Coppens wrote: Though I can't image the reason to put this question on this forum, Many of the systems made with gEDA tools have processors, and some of those are microcontrollers that GCC compiles C code. It's germain to coding gEDA tools and the systems developed with them too. I find comments like yours helpful, since most of my microcontroller experience has been in assembler and I'm learning C now for that, and to help with gEDA coding... John Griessen ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: C question
Thanks. I threw the question to the group because I know there's plenty of knowledgable people reading willing to answer it. Anyway, I was trying to get the compiler to generate 2 versions of an initialized array: ROM, and RAM. The processor I am using has more ROM than RAM, so placing the code into ROM makes more sense, yet I was having trouble getting access it correctly due to a routine expecting a const ptr. So, I was trying it in RAM, but not sure if the code was correct. Thanks again for the help :) gene - Original Message - From: John Griessen Date: Saturday, March 3, 2007 11:51 am Subject: Re: gEDA-user: C question To: gEDA user mailing list John Coppens wrote: Though I can't image the reason to put this question on this forum, Many of the systems made with gEDA tools have processors, and some of those are microcontrollers that GCC compiles C code. It's germain to coding gEDA tools and the systems developed with them too. I find comments like yours helpful, since most of my microcontroller experience has been in assembler and I'm learning C now for that, and to help with gEDA coding... John Griessen ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
Re: gEDA-user: C question
On Sat, Mar 03, 2007 at 11:57:36PM +, [EMAIL PROTECTED] wrote: Anyway, I was trying to get the compiler to generate 2 versions of an initialized array: ROM, and RAM. Declaring something const might do it, although some architectures like AVR address ROM and RAM differently, so you have to pay attention. The only way to be sure that data goes were you want it is to write a linker script. That will ensure that all of the data and code is organized the way you want. For example, for a network card I organized all of the primary functionality into a 'cached' section and used a link script to group that section together. By using one contiguous block of memory the processor is able to keep all of the code in its L1 icache. -- Ben Jackson AD7GD [EMAIL PROTECTED] http://www.ben.com/ ___ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
gEDA-user: C question
Look at the following:1) int bob[5] = {0x1, 0x2];2) int const bob[2] = {0x1,
0x2};3) static int const bob[2] = {0x1, 0x2};1 creates an initialized array in
ram.2 creates a read-only array - presumably in ROMWhat does 3 do? I think 3
compiles to a read-only area of ram. Am I correct?gene
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Re: gEDA-user: C question
On Sat, Mar 03, 2007 at 03:23:22AM +, [EMAIL PROTECTED] wrote:
Look at the following:1) int bob[5] = {0x1, 0x2];2) int const bob[2] = {0x1,
0x2};3) static int const bob[2] = {0x1, 0x2};1 creates an initialized array
in ram.2 creates a read-only array - presumably in ROMWhat does 3 do? I
think 3 compiles to a read-only area of ram. Am I correct?gene
static vs nothing (non-static, default) has to do with linking. A static
variable is not global and cannot be accessed from other modules (files,
basically) when compiling. It's basically hiding data and avoiding
namespace polution.
const vs nothing (non-const, default) determines whether you can modify
the data. The compiler may put the data somewhere different than it
would put other initialized data, or it may not. Where you put const
matters, because in one declaration different things might be protected.
For example,
const char *p; /* p points to 'const chars', an immutable string */
char const *p; /* the pointer p can't change, but the chars can */
const char const *p; /* neither p nor the chars it points at change */
So without looking it up, I'm not sure what your 'int const bob[]' means,
but you probably mean 'const int bob[]', the ints in bob don't change.
--
Ben Jackson AD7GD
[EMAIL PROTECTED]
http://www.ben.com/
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Re: gEDA-user: C question
On Sat, 03 Mar 2007 03:23:22 + (GMT)
[EMAIL PROTECTED] wrote:
Look at the following:1) int bob[5] = {0x1, 0x2];2) int const bob[2] =
{0x1, 0x2};3) static int const bob[2] = {0x1, 0x2};1 creates an
initialized array in ram.2 creates a read-only array - presumably in
ROMWhat does 3 do? I think 3 compiles to a read-only area of ram. Am
I correct?gene
Though I can't image the reason to put this question on this forum,
here's what I think:
'Static' is normally reserved to specify the data should never be
destroyed by the compiler if the compiler thinks it's not necessary any
more (eg. to make data 'static', i.e. available between function calls to
the same function).
'const' means the program shouldn't be able to change it. Like you said,
make it read-only.
John
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