GDB seems to set breakpoints on functions at the wrong place

[Andrew Cagney]

> I am writing a tool to print out the arguments passed to certain
> functions, and have based it on GDB, but have a problem where GDB
> sometimes sets the breakpoints before $ebp is set, and sometimes after
> which makes getting arguments difficult.
> 
> For example, the output below is from GDB 5.3 on Debian Sarge. In it I
> set breakpoints on both scanf and strcpy. The strcpy breakpoint is set
> after "mov %esp,%ebp" which seems to be the normal behaviour. This means I
> can get the second argument using "print *((char**)($ebp+0x08))", just
> as is done in the function. Whereas the breakpoint in scanf is set
> before the "%esp,%ebp" which means I have to get the arguments as if I
> am in the calling function - "print *((char**)($esp+0x04))"
> 
> I think this is a bug, but would like to check before reporting it.
> Any advice would be appreciated. Is there a reliable mechanism for
> finding the arguments to a function? Currently I am thinking about
> setting breakpoints at *function_name, which seems to consistently set
> breakpoints before $ebp is set. This is not as nice as doing it after
> (as it is different from the way arguments are used in the function),
> but since I am writing an automated tool, consistency is the most
> important thing.

Can you try reproducing this with a current (6.1.1) GDB?  GDB 5.3 is 
very old.

Andrew