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author | Tom Tromey <tromey@adacore.com> | 2022-02-16 10:07:18 -0700 |
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committer | Tom Tromey <tromey@adacore.com> | 2022-03-07 08:27:38 -0700 |
commit | 63fc2437deda87a566059444630ccc402945ae99 (patch) | |
tree | ff778d7fab7aea1716f23f4c36c5553d9c5c1449 /gdb/doc | |
parent | c9bfa277e9e6467dad91641357e09bf0a7ac0dc2 (diff) | |
download | fsf-binutils-gdb-63fc2437deda87a566059444630ccc402945ae99.zip fsf-binutils-gdb-63fc2437deda87a566059444630ccc402945ae99.tar.gz fsf-binutils-gdb-63fc2437deda87a566059444630ccc402945ae99.tar.bz2 |
Implement real literal extension for Ada
Sometimes it is convenient to be able to specify the exact bits of a
floating-point literal. For example, you may want to set a
floating-point register to a denormalized value, or to a particular
NaN.
In C, you can do this by combining the "{}" cast with an array
literal, like:
(gdb) p {double}{0x576488BDD2AE9FFE}
$1 = 9.8765449999999996e+112
This patch adds a somewhat similar idea to Ada. It extends the lexer
to allow "l" and "f" suffixes in a based literal. The "f" indicates a
floating-point literal, and the "l"s control the size of the
floating-point type.
Note that this differs from Ada's based real literals. I believe
those can also be used to control the bits of a floating-point value,
but they are a bit more cumbersome to use (simplest is binary but
that's also very lengthy). Also, these aren't implemented in GDB.
I chose not to allow this extension to work with based integer
literals with exponents. That didn't seem very useful.
Diffstat (limited to 'gdb/doc')
-rw-r--r-- | gdb/doc/gdb.texinfo | 16 |
1 files changed, 16 insertions, 0 deletions
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo index 5d1dcfd..063e3a1 100644 --- a/gdb/doc/gdb.texinfo +++ b/gdb/doc/gdb.texinfo @@ -18190,6 +18190,9 @@ context. Should your program redefine these names in a package or procedure (at best a dubious practice), you will have to use fully qualified names to access their new definitions. + +@item +Based real literals are not implemented. @end itemize @node Additions to Ada @@ -18248,6 +18251,19 @@ complex conditional breaks: (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100) @end smallexample +@item +An extension to based literals can be used to specify the exact byte +contents of a floating-point literal. After the base, you can use +from zero to two @samp{l} characters, followed by an @samp{f}. The +number of @samp{l} characters controls the width of the resulting real +constant: zero means @code{Float} is used, one means +@code{Long_Float}, and two means @code{Long_Long_Float}. + +@smallexample +(@value{GDBP}) print 16f#41b80000# +$1 = 23.0 +@end smallexample + @item Rather than use catenation and symbolic character names to introduce special characters into strings, one may instead use a special bracket notation, |