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| author | Eli Zaretskii <eliz@gnu.org> | 2005-04-27 13:02:15 +0000 |
|---|---|---|
| committer | Eli Zaretskii <eliz@gnu.org> | 2005-04-27 13:02:15 +0000 |
| commit | 18999be52807c17fc04235fac872eca39979a91e (patch) | |
| tree | 9877674e4ce6cd12f5a53e568508026b6af2d67e /gdb/doc | |
| parent | 8c19749adc5f155f7a51f1799cd3494851c75909 (diff) | |
| download | gdb-18999be52807c17fc04235fac872eca39979a91e.zip gdb-18999be52807c17fc04235fac872eca39979a91e.tar.gz gdb-18999be52807c17fc04235fac872eca39979a91e.tar.bz2 | |
* gdb.texinfo (Backtrace): Describe backtraces with arguments that
were optimized away.
Diffstat (limited to 'gdb/doc')
| -rw-r--r-- | gdb/doc/ChangeLog | 5 | ||||
| -rw-r--r-- | gdb/doc/gdb.texinfo | 29 |
2 files changed, 34 insertions, 0 deletions
diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog index 84e27e4..b965420 100644 --- a/gdb/doc/ChangeLog +++ b/gdb/doc/ChangeLog @@ -1,3 +1,8 @@ +2005-04-27 Eli Zaretskii <eliz@gnu.org> + + * gdb.texinfo (Backtrace): Describe backtraces with arguments that + were optimized away. + 2005-04-22 Eli Zaretskii <eliz@gnu.org> * gdb.texinfo (Remote configuration): Document "set/show diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 6e64c1a..de7b58a 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -4170,6 +4170,35 @@ The display for frame zero does not begin with a program counter value, indicating that your program has stopped at the beginning of the code for line @code{993} of @code{builtin.c}. +@cindex value optimized out, in backtrace +@cindex function call arguments, optimized out +If your program was compiled with optimizations, some compilers will +optimize away arguments passed to functions if those arguments are +never used after the call. Such optimizations generate code that +passes arguments through registers, but doesn't store those arguments +in the stack frame. @value{GDBN} has no way of displaying such +arguments in stack frames other than the innermost one. Here's what +such a backtrace might look like: + +@smallexample +@group +#0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8) + at builtin.c:993 +#1 0x6e38 in expand_macro (sym=<value optimized out>) at macro.c:242 +#2 0x6840 in expand_token (obs=0x0, t=<value optimized out>, td=0xf7fffb08) + at macro.c:71 +(More stack frames follow...) +@end group +@end smallexample + +@noindent +The values of arguments that were not saved in their stack frames are +shown as @samp{<value optimized out>}. + +If you need to display the values of such optimized-out arguments, +either deduce that from other variables whose values depend on the one +you are interested in, or recompile without optimizations. + @cindex backtrace beyond @code{main} function @cindex program entry point @cindex startup code, and backtrace |