Date: Fri, 30 Jun 2006 20:52:40 +0200 From: Ulrich <freebsd-alpha@infopuls.com> To: freebsd-alpha@freebsd.org Subject: 4.11 gdb/gcc problem with debugging simple C programs Message-ID: <20060630185240.17233.qmail@igel.cyberlink.ch> References: <Pine.GSO.4.58a.0509070037220.11377@uhunix2> <20060227231802.8883.qmail@igel.cyberlink.ch> <20060228020917.GA2778@xiao.rsnet> <20060228074937.GB39184@freebie.xs4all.nl>
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Hi everybody
While running a simple C program I noticed that gdb wasn't able to print out
the correct values of parameters. All parameter values were wrongly
displayed whenever gdb entered or left a function and automatically showed
the function's parameter list together with each parameter's value. Strange
enough the program works with the correct values and runs correctly. Using
gdb's print command also displays the wrong values. Sometimes even a pointer
value is displayed as null although the program works with a valid pointer.
The program was compiled without optimisation: gcc -Wall -g test1.c -o test1
Here are two short examples of what I see.
Starting program: ./test1 value1 value2 value3 value4
Breakpoint 1, main (ac=536872600, av=0x0) at test1.c:3
3 int main(int ac, char *av[]) {
(gdb) print ac
$1 = 536872600
The program can access the 4 parameter values and ac has the correct value.
Starting program: ./test2 -v 6000 -l 112233 file1 file2
Breakpoint 1, main (ac=536873548, av=0x7) at test2.c:75
75 int main(int ac, char *av[]) {
(gdb) print ac
$1 = 536873548
It seems that the addresses of parameters are shifted while accessed by gdb.
The value of parameter "av" is displayed as "0x7" which is the correct value
of "ac". I also don't know whether it means something that the wrong values
of "ac" in both examples start with the same sequence of digits "53687".
I'm reading the list since end of 2004 and I cannot remember that this
problem came up already. I also checked with google but didn't find anything
useful. Can someone drop me a hint where to search or what to do? I don't
think that gdb or gcc are faulty, but that I did something without noticing
it.
gcc version 2.95.4 20020320 [FreeBSD]
GNU gdb 4.18 (FreeBSD)
TIA
Ulrich
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