iffe: really abort on output{ fail (re: e20c0c6b, e72543a, b6bd981)

After further examining the iffe code I found that fail{ ... }end
as well as pass{ ... }end blocks are executed in iffe's current
environment, using a simple 'eval', with no safeguards whatsoever!

This does of course afford maximum flexibility... for example, a
block can 'exit 1' to abort the iffe run and the whole build with
it. We can use this to abort properly on fatal compilation errors.

src/cmd/INIT/iffe.sh:
- Complete the fail{ and pass{ documentation; it should really be
  known that they run in iffe's current environment.
- Make one change: for just the 'eval' command that runs these
  blocks, redirect standard error back to the saved $stderr file
  descriptor so these blocks can write error messages using the
  standard >&2 instead of the undocumented >&$stderr.

src/lib/**/features/*:
- Write error message to standard error and error out properly when
  an output{ ... }end block fails to compile, instead of writing an
  #error directive to error out later.

src/cmd/INIT/iffe.sh

@@ -32,7 +32,7 @@ AIX)	unset LIBPATH ;;
 esac
 
 command=iffe
-version=2021-12-22
+version=2021-12-31
 
 compile() # $cc ...
 {
@@ -873,8 +873,8 @@ case `(getopts '[-][123:xyz]' opt --xyz; echo 0$opt) 2>/dev/null` in
 	}
 [+?\abegin\a\b{\b ... \b}end\b delimit multiline code blocks that override
 	or augment the default code provided by \biffe\b. User supplied code
-	blocks should be compatible with the K&R, ANSI, and C++ C language
-	dialects for maximal portability. Test code may call the function
+	blocks should be compatible with the C89/C90 C language
+	standard for maximal portability. Test code may call the function
 	\bNOTE("...")\b to emit short text in \b--verbose\b output; only one
 	\bNOTE()\b should be called per test for readability. In addition to
 	all macro definitions generated by previous tests, all generated
@@ -1066,7 +1066,12 @@ case `(getopts '[-][123:xyz]' opt --xyz; echo 0$opt) 2>/dev/null` in
 	[+execute?The block is compiled, linked, and executed. \b0\b exit
 		status means success.]
 	[+fail?If the test fails then the block text is evaluated by
-		\bsh\b(1).]
+		\bsh\b(1) in \biffe\b'\'$'s current shell environment.
+		Changes in the shell state, such as variables, will survive the block.
+		Standard input is redirected to \b/dev/null\b.
+		Standard output is copied to the output file.
+		Standard error may be used to log informative or error messages.
+		The block may use \bexit\b to abort the \biffe\b run.]
 	[+link?The block is compiled and linked (\bcc -o\b).]
 	[+macro?The block is preprocessed (\bcc -E\b) and lines containing
 		text bracketed by \b<<"\b ... \b">>\b (\aless-than\a \aless-than\a
@@ -1080,7 +1085,7 @@ case `(getopts '[-][123:xyz]' opt --xyz; echo 0$opt) 2>/dev/null` in
 	[+output?The block is compiled, linked, and executed, and the output
 		is copied to the output file.]
 	[+pass?If the test succeeds then the block text is evaluated by
-		\bsh\b(1).]
+		\bsh\b(1) in the same manner as \bfail\b above.]
 	[+preprocess?The block is preprocessed (\bcc -E\b).]
 	[+run?The block is executed as a shell script and the output is
 		copied to the output file. Successful test macros are also
@@ -4543,7 +4548,8 @@ struct xxx* f() { return &v; }"
 		*)		user_pf=$pass user_yn=$yes ;;
 		esac
 		case $user_pf in
-		?*)	eval "$user_pf" <&$nullin ;;
+		?*)	# Run a pass{ or fail{ block in iffe's current environment
+			eval "$user_pf" <&$nullin 2>&$stderr ;;
 		esac
 		case $user_yn in
 		?*)	case $def in

src/cmd/builtin/features/pty

@@ -50,7 +50,8 @@ tst - -lm output{
 		return 0;
 	}
 }end fail{
-	echo '#error The output block in src/cmd/builtin/features/pty failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 extern	_getpty		char*		(int*, int, mode_t, int)

src/lib/libast/features/common

@@ -319,7 +319,8 @@ tst	- output{
 		return 0;
 	}
 }end fail{
-	echo '#error Output block #2 in src/lib/libast/features/common failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 tst	- -DN=1 - -DN=0 output{

src/lib/libast/features/float

@@ -890,7 +890,8 @@ tst	- note{ missing floating point limits }end output{
 		return 0;
 	}
 }end fail{
-	echo '#error Output block #1 in src/lib/libast/features/float failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 tst	- note{ double exponent bitfoolery }end output{
@@ -926,7 +927,8 @@ tst	- note{ double exponent bitfoolery }end output{
 		return 0;
 	}
 }end fail{
-	echo '#error Output block #2 in src/lib/libast/features/float failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 tst	- note{ long double exponent bitfoolery }end output{
@@ -962,7 +964,8 @@ tst	- note{ long double exponent bitfoolery }end output{
 		return 0;
 	}
 }end fail{
-	echo '#error Output block #3 in src/lib/libast/features/float failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 tst	- -DN=1 - -DN=2 note{ _ast_fltmax_t maximum integral type }end output{

src/lib/libast/features/lib

@@ -659,7 +659,8 @@ tst	- output{
 	}
 
 }end fail{
-	echo '#error The output block in src/lib/libast/features/lib failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 tst	no64 note{ largefile 64 broken }end execute{

src/lib/libast/features/sfio

@@ -15,7 +15,8 @@ tst	- note{ number of bits in pointer }end output{
 		return 0;
 	}
 }end fail{
-	echo '#error The output block in src/lib/libast/features/sfio failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end
 
 tst	tmp_rmfail note{ open files cannot be removed }end execute{

src/lib/libast/features/sizeof

@@ -11,5 +11,6 @@ tst	- note{ sizeof(integral-type) }end output{
 		return 0;
 	}
 }end fail{
-	echo '#error The output block in src/lib/libast/features/sizeof failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end

src/lib/libdll/features/dll

@@ -261,5 +261,6 @@ tst	- -lm output{
 		return 0;
 	}
 }end fail{
-	echo '#error The output block in src/lib/libdll/features/dll failed to compile. Rebuild with IFFEFLAGS=-d1 to debug.'
+	echo "$0: Output block failed to compile. Export IFFEFLAGS=-d1 to debug." >&2
+	exit 1
 }end