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author | Andrew Burgess <andrew.burgess@embecosm.com> | 2023-02-10 23:49:19 +0000 |
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committer | Maciej W. Rozycki <macro@embecosm.com> | 2023-02-10 23:49:19 +0000 |
commit | a0c07915778486a950952139d27c01d4285b02b4 (patch) | |
tree | 4dec76630c699133cf45932f1aa6781bc7255a75 /gdb/doc/gdb.texinfo | |
parent | a2fb245a4b81ffdc93a9c6e9ceddbfb323ac9bec (diff) | |
download | binutils-gdb-a0c07915778486a950952139d27c01d4285b02b4.tar.gz |
GDB: Introduce limited array lengths while printing values
This commit introduces the idea of loading only part of an array in
order to print it, what I call "limited length" arrays.
The motivation behind this work is to make it possible to print slices
of very large arrays, where very large means bigger than
`max-value-size'.
Consider this GDB session with the current GDB:
(gdb) set max-value-size 100
(gdb) p large_1d_array
value requires 400 bytes, which is more than max-value-size
(gdb) p -elements 10 -- large_1d_array
value requires 400 bytes, which is more than max-value-size
notice that the request to print 10 elements still fails, even though 10
elements should be less than the max-value-size. With a patched version
of GDB:
(gdb) p -elements 10 -- large_1d_array
$1 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9...}
So now the print has succeeded. It also has loaded `max-value-size'
worth of data into value history, so the recorded value can be accessed
consistently:
(gdb) p -elements 10 -- $1
$2 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9...}
(gdb) p $1
$3 = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
20, 21, 22, 23, 24, <unavailable> <repeats 75 times>}
(gdb)
Accesses with other languages work similarly, although for Ada only
C-style [] array element/dimension accesses use history. For both Ada
and Fortran () array element/dimension accesses go straight to the
inferior, bypassing the value history just as with C pointers.
Co-Authored-By: Maciej W. Rozycki <macro@embecosm.com>
Diffstat (limited to 'gdb/doc/gdb.texinfo')
-rw-r--r-- | gdb/doc/gdb.texinfo | 9 |
1 files changed, 9 insertions, 0 deletions
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 7b128053b5a..0beb45857c3 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -11759,6 +11759,14 @@ When @value{GDBN} starts, this limit is set to 200. Setting @var{number-of-elements} to @code{unlimited} or zero means that the number of elements to print is unlimited. +When printing very large arrays, whose size is greater than +@code{max-value-size} (@pxref{set max-value-size,,max-value-size}), +if the @code{print elements} is set such that the size of the elements +being printed is less than or equal to @code{max-value-size}, then +@value{GDBN} will print the array (up to the @code{print elements} limit), +and only @code{max-value-size} worth of data will be added into the value +history (@pxref{Value History, ,Value History}). + @item show print elements Display the number of elements of a large array that @value{GDBN} will print. @@ -14174,6 +14182,7 @@ may indicate a value that is incorrectly large, this in turn may cause @value{GDBN} to try and allocate an overly large amount of memory. @table @code +@anchor{set max-value-size} @kindex set max-value-size @item set max-value-size @var{bytes} @itemx set max-value-size unlimited |