Messages in this thread | | | Date | Fri, 06 Jun 2003 13:27:35 -0400 | From | Timothy Miller <> | Subject | Kernel printk format string compression: C syntax problem |
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Some of you may recall that I've been working on a way to compress kernel printk format strings so as to shrink the kernel memory image a bit. My results so far are that given the amount of space required for all kernel strings, I can compress them to half their original size. Given something the size of an allyesconfig kernel, that's not much compression over-all, but it's still interesting. Additionally, the means to compress the kernel messages are a compile-time issue and completely transparent to the coder.
I am, however, encountering a problem, and I was hoping some people who know C syntax better than both myself and the C syntax spec I found at "http://eic.sourceforge.net/iso_c.html" could help me solve it.
Here's an example of the problem:
This line from process.c starts out as:
printk("EIP: %04x:[<%08lx>] CPU: %d\n",0xffff & regs->xcs,regs->eip, (current_thread_info()->cpu));
And is replaced by:
printk( "EIP\200\3164x:[<\3168lx>] CPU\200%d\n" ,0xffff & regs->xcs,regs->eip, (current_thread_info()->cpu));
GCC 3.0.4 makes the following complaint:
arch/i386/kernel/process.c:173: warning: too many arguments for format
What I believe is happening is that where I have the escape code "\316" concatenated with the literal "8", the compiler is seeing it as "\3168" and doesn't want to take it. Now, it's just a warning, and it MAY be doing the right thing, but what I want to know is the PROPER UNAMBIGUOUS way to specify at 3-digit octal escape code which is followed immediately by a literal digit.
Any suggestions?
Thank you.
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