[git commit] bc: trim config help text, add a few comments, no code changes
Denys Vlasenko
vda.linux at googlemail.com
Thu Dec 13 15:35:52 UTC 2018
commit: https://git.busybox.net/busybox/commit/?id=89e785af98acb71ae495c76e1f1cf4944431a3db
branch: https://git.busybox.net/busybox/commit/?id=refs/heads/master
Signed-off-by: Denys Vlasenko <vda.linux at googlemail.com>
---
miscutils/bc.c | 88 +++++++++++++++++++++++++---------------------------------
1 file changed, 38 insertions(+), 50 deletions(-)
diff --git a/miscutils/bc.c b/miscutils/bc.c
index c7e0e39e0..47acd7fc3 100644
--- a/miscutils/bc.c
+++ b/miscutils/bc.c
@@ -10,49 +10,34 @@
//config: bc is a command-line, arbitrary-precision calculator with a
//config: Turing-complete language. See the GNU bc manual
//config: (https://www.gnu.org/software/bc/manual/bc.html) and bc spec
-//config: (http://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html)
-//config: for details.
+//config: (http://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html).
//config:
-//config: This bc has four differences to the GNU bc:
-//config:
-//config: 1) The period (.) can also be used as a shortcut for "last", as in
-//config: the BSD bc.
+//config: This bc has five differences to the GNU bc:
+//config: 1) The period (.) is a shortcut for "last", as in the BSD bc.
//config: 2) Arrays are copied before being passed as arguments to
//config: functions. This behavior is required by the bc spec.
//config: 3) Arrays can be passed to the builtin "length" function to get
-//config: the number of elements currently in the array. The following
-//config: example prints "1":
-//config:
-//config: a[0] = 0
-//config: length(a[])
-//config:
+//config: the number of elements in the array. This prints "1":
+//config: a[0] = 0; length(a[])
//config: 4) The precedence of the boolean "not" operator (!) is equal to
-//config: that of the unary minus (-), or negation, operator. This still
+//config: that of the unary minus (-) negation operator. This still
//config: allows POSIX-compliant scripts to work while somewhat
//config: preserving expected behavior (versus C) and making parsing
//config: easier.
+//config: 5) "read()" accepts expressions, not only numeric literals.
//config:
//config: Options:
-//config:
//config: -i --interactive force interactive mode
+//config: -q --quiet don't print version and copyright
+//config: -s --standard error if any non-POSIX extensions are used
+//config: -w --warn warn if any non-POSIX extensions are used
//config: -l --mathlib use predefined math routines:
-//config:
-//config: s(expr) = sine of expr in radians
-//config: c(expr) = cosine of expr in radians
-//config: a(expr) = arctangent of expr, returning
-//config: radians
-//config: l(expr) = natural log of expr
-//config: e(expr) = raises e to the power of expr
-//config: j(n, x) = Bessel function of integer order
-//config: n of x
-//config:
-//config: -q --quiet don't print version and copyright.
-//config: -s --standard error if any non-POSIX extensions are used.
-//config: -w --warn warn if any non-POSIX extensions are used.
-//config: -v --version print version and copyright and exit.
-//config:
-//config: Long options are only available if FEATURE_BC_LONG_OPTIONS is
-//config: enabled.
+//config: s(expr) sine in radians
+//config: c(expr) cosine in radians
+//config: a(expr) arctangent, returning radians
+//config: l(expr) natural log
+//config: e(expr) raises e to the power of expr
+//config: j(n, x) Bessel function of integer order n of x
//config:
//config:config DC
//config: bool "dc (38 kb; 49 kb when combined with bc)"
@@ -61,33 +46,24 @@
//config: dc is a reverse-polish notation command-line calculator which
//config: supports unlimited precision arithmetic. See the FreeBSD man page
//config: (https://www.unix.com/man-page/FreeBSD/1/dc/) and GNU dc manual
-//config: (https://www.gnu.org/software/bc/manual/dc-1.05/html_mono/dc.html)
-//config: for details.
+//config: (https://www.gnu.org/software/bc/manual/dc-1.05/html_mono/dc.html).
//config:
//config: This dc has a few differences from the two above:
-//config:
-//config: 1) When printing a byte stream (command "P"), this bc follows what
+//config: 1) When printing a byte stream (command "P"), this dc follows what
//config: the FreeBSD dc does.
-//config: 2) This dc implements the GNU extensions for divmod ("~") and
+//config: 2) Implements the GNU extensions for divmod ("~") and
//config: modular exponentiation ("|").
-//config: 3) This dc implements all FreeBSD extensions, except for "J" and
-//config: "M".
+//config: 3) Implements all FreeBSD extensions, except for "J" and "M".
//config: 4) Like the FreeBSD dc, this dc supports extended registers.
//config: However, they are implemented differently. When it encounters
//config: whitespace where a register should be, it skips the whitespace.
//config: If the character following is not a lowercase letter, an error
//config: is issued. Otherwise, the register name is parsed by the
//config: following regex:
-//config:
-//config: [a-z][a-z0-9_]*
-//config:
+//config: [a-z][a-z0-9_]*
//config: This generally means that register names will be surrounded by
-//config: whitespace.
-//config:
-//config: Examples:
-//config:
-//config: l idx s temp L index S temp2 < do_thing
-//config:
+//config: whitespace. Examples:
+//config: l idx s temp L index S temp2 < do_thing
//config: Also note that, like the FreeBSD dc, extended registers are not
//config: allowed unless the "-x" option is given.
//config:
@@ -105,11 +81,19 @@
//config: NOTE: This will require libm to be present for linking.
//config:
//config:config FEATURE_BC_SIGNALS
-//config: bool "Enable bc/dc signal handling"
+//config: bool "Interactive mode (+4kb)"
//config: default y
//config: depends on (BC || DC) && !FEATURE_DC_SMALL
//config: help
-//config: Enable signal handling for bc and dc.
+//config: Enable interactive mode: when started on a tty,
+//config: ^C interrupts execution and returns to command line,
+//config: errors also return to command line instead of exiting,
+//config: line editing with history is available.
+//config:
+//config: With this option off, input can still be taken from tty,
+//config: but all errors are fatal, ^C is fatal,
+//config: tty is treated exactly the same as any other
+//config: standard input (IOW: no line editing).
//config:
//config:config FEATURE_BC_LONG_OPTIONS
//config: bool "Enable bc/dc long options"
@@ -7468,6 +7452,8 @@ static int bc_vm_init(const char *env_len)
bc_program_init();
bc_parse_create(&G.prs, BC_PROG_MAIN);
+//TODO: in GNU bc, the check is (isatty(0) && isatty(1)),
+//-i option unconditionally enables this regardless of isatty():
if (isatty(0)) {
#if ENABLE_FEATURE_BC_SIGNALS
G_ttyin = 1;
@@ -7476,10 +7462,12 @@ static int bc_vm_init(const char *env_len)
// In particular, this means ^C won't cause
// stdout to get into "error state" if SIGINT hits
// within write() syscall.
- // The downside is that ^C while line input is taken
+ //
+ // The downside is that ^C while tty input is taken
// will only be handled after [Enter] since read()
// from stdin is not interrupted by ^C either,
// it restarts, thus fgetc() does not return on ^C.
+ // (This problem manifests only if line editing is disabled)
signal_SA_RESTART_empty_mask(SIGINT, record_signo);
// Without SA_RESTART, this exhibits a bug:
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