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| -rw-r--r-- | gdb/doc/ChangeLog | 4 | ||||
| -rw-r--r-- | gdb/doc/stabs.texinfo | 62 |
2 files changed, 37 insertions, 29 deletions
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index 3411981..44a1ace 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,7 @@ +Mon Apr 19 08:00:51 1993 Jim Kingdon (kingdon@cygnus.com) + + * stabs.texinfo (Parameters): Re-do "local parameters" section. + Sun Apr 18 09:47:45 1993 Jim Kingdon (kingdon@cygnus.com) * stabs.texinfo (Symbol descriptors): Re-do using @table and @xref. diff --git a/gdb/doc/stabs.texinfo b/gdb/doc/stabs.texinfo index fc19d5e..918459c 100644 --- a/gdb/doc/stabs.texinfo +++ b/gdb/doc/stabs.texinfo @@ -984,52 +984,56 @@ The stab for @code{s_flap} is located just before the @code{N_LBRAC} for @section Parameters The symbol descriptor @samp{p} is used to refer to parameters which are -in the arglist. They follow the symbol that represents the procedure -itself. The value of the symbol is the offset relative to the argument -list. - -If the parameter is passed in a register, or is allocated as a local -variable rather than an argument (the latter distinction is important -for machines in which the argument list offset is relative to something -different from a local variable offset), then the traditional way to do +in the arglist. Symbols have symbol type @samp{N_PSYM}. The value of +the symbol is the offset relative to the argument list. + +If the parameter is passed in a register, then the traditional way to do this is to provide two symbols for each argument: @example -.stabs "arg:p1" . . . -.stabs "arg:r1" . . . +.stabs "arg:p1" . . . ; N_PSYM +.stabs "arg:r1" . . . ; N_RSYM @end example Debuggers are expected to use the second one to find the value, and the first one to know that it is an argument. -Because this is kind of ugly, some compilers use symbol descriptor @samp{P} -or @samp{R} to indicate an argument which is in a register. The symbol -value is the register number. @samp{P} and @samp{R} mean the same -thing, the difference is that @samp{P} is a GNU invention and @samp{R} -is an IBM (xcoff) invention. As of version 4.9, GDB should handle -either one. - -There is no symbol descriptor analogous to @samp{P} for local variables. -Some compilers are said to use the pair of symbols approach described -above, but I don't know which ones. On the intel 960, the type of the -variable indicates whether a @samp{p} symbol's value is an the argument -list offset or a local variable offset. +Because this is kind of ugly, some compilers use symbol descriptor +@samp{P} or @samp{R} to indicate an argument which is in a register. +The symbol value is the register number. @samp{P} and @samp{R} mean the +same thing, the difference is that @samp{P} is a GNU invention and +@samp{R} is an IBM (xcoff) invention. As of version 4.9, GDB should +handle either one. Symbol type @samp{C_RPSYM} is used with @samp{R} and +@samp{N_RSYM} is used with @samp{P}. + +There is another case similar to an argument in a register, which is an +argument which is actually stored as a local variable. The only case I +know of where this happens is when the argument was passed in a register +and then the compiler stores it as a local variable. In this case the +compiler would probably be much better off claiming that it's in a +register, but at least in one case this isn't done. Some compilers are +said to use the pair of symbols approach described above ("arg:p" +followed by "arg:"), but I don't which if any. GCC, at least on the +960, uses a @samp{p} symbol descriptor for this case but uses +@samp{N_LSYM} instead of @samp{N_PSYM} to distinguish it. In this case +the value of the symbol is an offset relative to the local variables for +that function, not relative to the arguments. As a simple example, the code @example -17 main (argc, argv) -18 int argc; -19 char **argv; -20 @{ +main (argc, argv) + int argc; + char **argv; +@{ @end example produces the stabs @example -94 .stabs "main:F1",36,0,0,_main ; 36 is N_FUN -95 .stabs "argc:p1",160,0,0,68 ; 160 is N_PSYM -96 .stabs "argv:p20=*21=*2",160,0,0,72 +.stabs "main:F1",36,0,0,_main ; 36 is N_FUN +.stabs "argc:p1",160,0,0,68 ; 160 is N_PSYM +.stabs "argv:p20=*21=*2",160,0,0,72 @end example The type definition of argv is interesting because it contains several |