assembly in future C standard HCF Gerry Wheeler

c

    Sponsored Links

    Next

  • 1. Linked list allocation
    Consider implementing a (doubly) linked list. The simplest strategy is to provide functions item_t add_item(item_t predecessor); void delete_item(item_t item); where add_item allocates memory for a new list item and returns it (or NULL), and delete_item frees that memory. However, if at startup the program immediately adds a large number of items to a list, then all those calls to malloc() become expensive. An alternative I thought of was that add_item should allocate a block, say of size (100 * size-needed-by-an-item), then use pointers inside this block until the time comes to allocate a new block for 100 items. The problem with this is that deleting items becomes a mess - you can only free a block when all 100 items in it have been deleted, so in the worst case (where the programmer allocates 101 items, frees 99, adds 101, ...) you end up with for all intents and purposes a memory leak. Is there a better solution?
  • 2. Send and receive information between Excel/VBA and C
    Hi I use a large txt file of 1,5m lines which VBA reads into memory, and then can searches certain values out of that data. Seach could be faster and I wonder if c or some other language could be used for the search engine. So, Excel/VBA would send a variable and a big array to C, which would search given variable from the array, and return much smaller array of hits back to VBA. Is this possible? How? Any kind of help needed Regards, Jari
  • 3. while(!FP.eof()) is reading the last data point of the file twice
    I'm wondering if someone could point me to the flaw in the following code that uses the while(!FP.eof()) condition to read the input data. This condition is reading the last data point of the file twice. #include <iostream> #include <fstream> using namespace std; int main(int argc, char **argv) { double x; ifstream FP("test.d"); //while(!FP.eof()){FP >> x; cout << x << endl;} // This reads the last data point of test.d twice while(FP >> x){cout<< x << endl;} // This doesn't. return 0; } /* Using either gcc 3.4.6 or gcc 4.1.3 File "test.d" has the following 2 data points: 1.1 2.2 */ Thanks...ramana

Re: assembly in future C standard HCF Gerry Wheeler

Postby Walter Banks » Sat, 04 Nov 2006 22:35:39 GMT

As this thread wanders off topic this industry was introduced to a new
mnemonic in Byte article about decoding the undocumented
Motorola 6800 instructions. The HCF (Halt Catch Fire) opcode $DD
or $D9. HFC locked up the processor and cycled the address bus
The author of that article was Gerry Wheeler.

Gerry Wheeler, 54, died October 15, 2006, advanced non-Hodgkins
lymphoma cancer. Gerry made significant contributions to the technology
of the embedded systems world and was a key part of the development
of many household name products.

Programmer, Ham KG4NBB, author, father, husband, active commuity
participant Gerry will be missed by all.

w..


Similar Threads:

1.assembly in future C standard

Peter Nilsson < XXXX@XXXXX.COM > wrote:

(Crossposted to comp.std.c, with followups directed there, hopefully
 appropriately.  The original post discussed the possibility of whether
 __asm or something similar to it would be added to the C standard.)

> Contrary to Richard Heathfield's categorical statement, it is not an
> absolute given that there will never be an asm keyword in C. But it
> is unlikely because it's already clear that the asm keyword in C++ has
> not served to truly standardise the syntax of inline assembly.

One idea that was not mentioned in the original thread (I imagine for
good reason, because it's a half-baked and probably stupid idea that
occurred to me reading your post) would be to allow for some kind of
conditional assembly, just perhaps something like

#pragma assemble
#pragma X86 /* Inner pragma's implementation-defined */
  /* Inline assembly, which the implementation can ignore or not */
#pragma no-assemble
  /* Stock C code for implementations that can't or won't accept the
   * assemble pragma: */
  for( i=1; i < 10; i++ ) {
    foo();
    /* ... */
  }
#pragma end-assemble

The end result would be something like "If the implementation attempts
to inline the assembly code contained within a #pragma assemble
directive, the behavior is implementation-defined.  Otherwise the
assembly code shall be ignored and the C code contained within any
corresponding #pragma no-assemble directive shall be compiled as
though no directives were present."  It would require adding some
duties to the #pragma directive, but it would allow implementors to
take a reasonable shot at using targetted assembly instructions when
appropriate and available, and reverting to ordinary C otherwise.

I'm sure there are reasons why this is stupid and/or impossible, or it
would have been done already :-)

> At the end of the day, the committee could probably spend many man
> weeks deciding issues on an __asm keyword, but for what? Most
> implementations will keep their existing syntax, and most programmers
> who use inline assembly will no doubt continue to prefer the localised
> syntax because it's less cumbersome than any standard syntax.

Indeed, but it's an interesting thought experiment to consider how the
committee *might* add assembly to C if they chose to do so.  (Well,
interesting to me, at least.)

-- 
C. Benson Manica           | I *should* know what I'm talking about - if I
cbmanica(at)gmail.com      | don't, I need to know.  Flames welcome.



Return to c

 

Who is online

Users browsing this forum: No registered users and 53 guest