halcompile: reject declarations that export the same HAL name (2.9 backport)

docs/man/man1/halcompile.1

@@ -76,7 +76,13 @@ Install \fB.c\fR and \fB.py\fR files into the proper directory for HAL non-realt
 Extract documentation from \fB.comp\fR files into \fB.9\fR manpage files in the proper system directory (the \fB\-\-install\fR flag), which may require \fIsudo\fR to write to system directories.
 .IP \(bu 4
 Preprocess \fB.comp\fR files into \fB.c\fR files (the \fB\-\-preprocess\fR flag)
-.SH "SEE ALSO"
+.SH NAMES
+A name declared in a \fB.comp\fR file is a C identifier, but it is exported under a mangled HAL identifier: underscores become dashes, and a trailing dash or period is removed.
+\fBpin in float my_input\fR is reached from HAL as \fBcomponent.N.my\-input\fR, and \fBloadrt my_comp\fR exports its pins under \fBmy\-comp.N.\fR
+Two declarations that mangle to the same HAL name are rejected.
+.PP
+See HALNAME under \fISyntax\fR in the \fIHalcompile HAL Component Generator\fR documentation for the full rules.
+.SH "SEE ALSO\"
 \fIHalcompile HAL Component Generator\fR in the LinuxCNC documentation for a full description of the \fB.comp\fR syntax, along with examples
 
 \fBpydoc, HAL\fR and \fICreating Non-realtime Python Components\fR in the LinuxCNC documentation for documentation on the Python interface to HAL components

docs/src/hal/comp.adoc

@@ -229,6 +229,11 @@ A trailing "_" is retained, so that HAL identifiers which would otherwise collid
 |x.##    | x(MM)        | x.MM
 |===
 
+[NOTE]
+Two declarations that produce the same HAL identifier -- 'x_y_z' and 'x_y_z_' in
+the table above -- are rejected by `halcompile`; they would otherwise fail at
+`loadrt` with "HAL: ERROR: duplicate variable".
+
 * 'if CONDITION' - An expression involving the variable 'personality' which is nonzero when the pin or parameter should be created.
 
 * 'SIZE' - A number that gives the size of an array. The array items are numbered from 0 to 'SIZE'-1.

src/hal/utils/halcompile.g

@@ -151,13 +151,15 @@ deprecated = ['s32', 'u32']
 
 def initialize():
     global functions, params, pins, comp_name, names, docs, variables
-    global modparams, includes
+    global modparams, includes, hal_pin_names, hal_funct_names
 
     functions = []; params = []; pins = []; options = {}; variables = []
     modparams = []; docs = []; includes = [];
     comp_name = None
 
     names = {}
+    hal_pin_names = {}
+    hal_funct_names = {}
 
 def Warn(msg, *args):
     if args:
@@ -215,10 +217,25 @@ def check_name_ok(name):
     if name in names:
         Error("Duplicate item name %s" % name)
 
+def check_hal_name(seen, name):
+    """A declaration is a C identifier, but it is exported under a mangled HAL
+    identifier.  check_name_ok() only compares declared names, so two
+    declarations that mangle to one HAL name would compile cleanly and fail
+    later, at loadrt, with "HAL: ERROR: duplicate variable"."""
+    if name == "_": return              # the unnamed singleton function
+    hal_name = to_hal(name)
+    if hal_name in seen:
+        Error("'%s' and '%s' both export the HAL name '%s'; see HALNAME under "
+              "'Syntax' in the Halcompile HAL Component Generator "
+              "documentation, https://linuxcnc.org/docs/html/hal/comp.html"
+              % (seen[hal_name], name, hal_name))
+    seen[hal_name] = name
+
 def pin(name, type, array, dir, doc, value, personality):
     checkarray(name, array)
     type = type2type(type)
     check_name_ok(name)
+    check_hal_name(hal_pin_names, name)
     docs.append(('pin', name, type, array, dir, doc, value, personality))
     names[name] = None
     pins.append((name, type, array, dir, value, personality))
@@ -227,12 +244,15 @@ def param(name, type, array, dir, doc, value, personality):
     checkarray(name, array)
     type = type2type(type)
     check_name_ok(name)
+    check_hal_name(hal_pin_names, name) # hal_lib.c: setp cannot tell a pin
+                                        # and a param of one name apart
     docs.append(('param', name, type, array, dir, doc, value, personality))
     names[name] = None
     params.append((name, type, array, dir, value, personality))
 
 def function(name, fp, doc):
     check_name_ok(name)
+    check_hal_name(hal_funct_names, name)
     docs.append(('funct', name, fp, doc))
     names[name] = None
     functions.append((name, fp))

tests/halcompile/halname/.gitignore

@@ -0,0 +1 @@
+halname_mangled.c

tests/halcompile/halname/expected

@@ -0,0 +1,3 @@
+halname_collision.comp:4:18: 'x_y' and 'x_y_' both export the HAL name 'x-y'; see HALNAME under 'Syntax' in the Halcompile HAL Component Generator documentation, https://linuxcnc.org/docs/html/hal/comp.html
+>  pin out bit x_y_;
+>                   ^

tests/halcompile/halname/halname_collision.comp

@@ -0,0 +1,7 @@
+component halname_collision;
+license "GPL";
+pin in bit x_y;
+pin out bit x_y_;
+function _;
+;;
+FUNCTION(_) {}

tests/halcompile/halname/halname_mangled.comp

@@ -0,0 +1,6 @@
+component halname_mangled;
+license "GPL";
+pin in bit my_pin;
+function _;
+;;
+FUNCTION(_) {}

tests/halcompile/halname/test.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+set -e
+
+# A name that is exported under a different HAL name must still compile.
+rm -f halname_mangled.c
+halcompile --preprocess halname_mangled.comp 2>&1
+test -f halname_mangled.c || echo 'halcompile failed to produce halname_mangled.c'
+
+# Two declarations that mangle to one HAL name must be rejected, not left to
+# fail at loadrt as "HAL: ERROR: duplicate variable".
+rm -f halname_collision.c
+if halcompile --preprocess halname_collision.comp 2>&1; then
+    echo 'halcompile erroneously accepted halname_collision.comp'
+fi
+test ! -f halname_collision.c || echo 'halcompile erroneously produced halname_collision.c'