Release notes for Jam/MR 2.4 (aka Jam - make(1) redux) 1. Release info: Jam/MR 2.4 March, 21, 2002 VERSION 2.4 2. Compatibility Jam 2.4 is upward compatible with Jam 2.3 The Jam 2.4 language is a superset of the 2.3 language; Jamfiles, Jambase, and other rulesets used in 2.3 can be used with the 2.4 language support. 3. Changes since 2.3. 3.1. Changes to Jam Language The mechanism for calling rules that return values - "[ rule args ...]", (and 'return' in the rule body), is now a documented part of the language. Add "on ..." syntax, to invoke a rule under the influence of a target's specific variables. Add "[ on targ rule ... ]" to call a rule returning a value, under the influence of a target's specific variables. New 'Glob' builtin that returns a list of files, given a list of directories, and a list of filename patterns. New 'while expr { block }' construct. New :E=value modifier provides default value if variable unset. New :J=joinval modifier concatenates list elements into single element, separated by joinval. \ can now be used to escape a space (or any single whitespace character), so that you don't have to resort to quotes. New 'Match regexp : string' rule matches regexp against string and returns list of results. Rules can now be invoked indirectly, through variable names. If the variable expands to an empty list, no rule is run. If the variable expands to multiple entries, each rule is run with the same arguments. The result of the rule invocation is the concatenation of the results of the rules invoked. 'Echo' and 'Exit' now have aliases 'echo' and 'exit', since it is really hard to tell that these are built-in rules and not part of the language, like 'include'. Real rules continue to start with a capital. 3.2. Jambase Changes Support for YACCGEN, the suffix used on generated yacc output. Fix ups to have jam and p4 build with borland C 5.5, and minor win98 jam support for jam clean SubDirHdrs now takes directory names in the same format as SubInclude : one directory element per word. More portable support for specifying includes and #defines: New ASHDRS, CCHDRS, CCDEFS, DEFINES, ObjectDefines, FQuote, FIncludes, FDefines. Ordering of cc and c++ flags grossly rearranged. Jambase has been compacted by applying the new E: and J: expansion modifiers. New SoftLink rule, courtesy of David Lindes. It currently assumes you can pass a -s flag to $(LN). 3.3 'jam' Changes (See Jam.html) Added '-q' (quit quick) option; jam will exit promptly (as if it received an interrupt), as soon as any target fails. Added experimental '-g' (build newest sources first) option: all things being equal, normally targets are simply built in the order they appear in the Jamfiles. With this flag, targets with the newest sources are built first. From an idea by Arnt Gulbrandsen. Undocumented (outside this note). 3.4. Jam internal code changes jamgram.yy now defines YYMAXDEPTH to 10000, what it is on FreeBSD, for older yaccs that left it at 150 or so. This is needed for the right-recursion now used in the grammar. Optimize rule compilation, with right-recursion instead of left. Split jam's built-in rules out to builtins.c from compile.c, so that compile.c only deals with the language. Split jam's pathsys.h from filesys.h, since they are really two different pieces. evaluate_if(), which evaluated the condition tree for 'if' and returned an int, has been replaced with compile_eval(), which does essentially the same but returns a LIST. 4. Fixed bugs Missing TEMPORARY targets with multiple parents no longer spoil one parent's time with another. The parents' time is used for comparison with dependents, but no longer taken on as the target's own time. 'actions updated', not 'actions together', now protects targets from being deleted on failed/interrupted updates. Fixed broken $(v[1-]), which always returned an empty expansion. Thanks to Ian Godin . Defining a rule within another rule, and invoking the enclosing rule more than once, would result in giving the first rule a null definition. Fixed. $(d:P) now works properly on the mac, climbing up directories. Thanks to Miklos Fazekas . No longer (sometimes) treat \ as a directory separator on UNIX. It isn't supposed to be, but was due to bungled ifdefs. Applying just :U or :D (or :E, :J) mods no longer causes the variable value to be treated as a filename (parsed and rebuilt using the OS specific pathsys routines). Previously, if _any_ mods were present then the value was parsed and rebuilt as if a filename, and that could in certain cases munge the value. Only the file modifiers (:GDBSM) treat the value as a filename. Four rules makeCommon, makeGrist, makeString, makeSubDir from jam 2.2 missing in 2.3 have been re-added, with apologies to dtb@cisco.com. Return status more likely to be correct when using -d0, now that targets are could as being built even with no debugging output. Thanks to Miklos Fazekas . yyacc now suffixes all terminals it defines with _t, so that they don't conflict with other symbols (like RULE with the typedef in rules.h). Thanks to Michael Allard. InstallInto now handles multiple sources properly, rather than acting as if each installed target depended on all sources to be installed. $(INSTALLGRIST) is now the default grist for installed targets, rather than the hardcoded 'installed'. Thanks to Stephen Goodson. 5. Porting [MACINTOSH] Paths are now downshifted (internally) so as to handle its case insensitivity. Thanks to Miklos Fazekas . [NT] MS changed the macro for the IA64 Windows NT 64bit compiler. [CYGWIN] Cygwin jam porting: dance around bison and yyacc. Use bison's -y flag to use yacc's output file naming conventions, and don't use yyacc on systems whose SUFEXE is set. [VMS] The Jambase itself was not formatting the CCHDRS and CCDEFS properly: on VMS they can't be appended to, because multiple /define or /include directives don't work. Instead now CCHDRS and CCDEFS is reformatted from HDRS and DEFINES anytime those latter two change. This requires the recent change to jam to allow access to target-specific variables when setting other variables. [VMS] Remove exception call when file_dirscan() can't, for some reason, scan a directory. Use a better set of #ifdefs to determine if we're on a vax, rather than relying on the C compiler being a specific version: we're able to build with the C++ compiler now. [VMS] Port new jam to run with just cxx compiler. (The C compiler being a extra-cost item). [NT] Add entry for DevStudio when the settings are already in the system environment. [NT] default $(MV) to "move /y" in Jambase. [MINGW] Mingw port by Max Blagai. =============================================================================== =============================================================================== Release notes for Jam/MR 2.3 (aka Jam - make(1) redux) 0. Bugs fixed since 2.3.1 PATCHLEVEL 2 - 3/12/2001 NOCARE changed back: it once again does not applies to targets with sources and/or actions. In 2.3 it was changed to apply to such targets, but that broke header file builds: files that are #included get marked with NOCARE, but if they have source or actions, they still should get built. 1. Release info: Jam/MR 2.3 November 16, 2000 VERSION 2.3 PATCHLEVEL 1 2. Compatibility Jam 2.3 is upward compatible with Jam 2.2. The Jam 2.3 language is a superset of the 2.2 language; Jamfiles, Jambase, and other rulesets used in 2.2 can be used with the 2.3 language support. 3. Changes since 2.2 3.1. Changes to Jam Language Rules now can have values, which can expanded into a list with the new "[ rule args ... ]" syntax. A rule's value is the value of its last statement, though only the following statements have values: if (value of the leg chosen), switch (ditto), set (value of the resulting variable), return (its arguments). Note that 'return' doesn't actually return. This support is EXPERIEMENTAL and otherwise undocumented. (2.3.1) Because of the new way lists are processed, if a rule has no targets a warning message is no longer issued. NOCARE now applies to targets with sources and/or actions, rather than just those without. 3.2. Jambase Changes The HDRPATTERN variable now allows for leading blanks before the #include, to keep up with ANSI. By john@nanaon-sha.co.jp (John Belmonte) (2.2.3). HDRPATTERN has been adjusted to avoid mistaking cases like: # include /* could be */ MkDir now NOUPDATE's $(DOT), so that there are no dependencies on the current directory's timestamp. By john@nanaon-sha.co.jp (John Belmonte). The old mock functions like makeDirName, which assigned their results to the variable named as their first argument, have been replaced with real functions using the new [] synxtax. E.g. "makeDirName foo : bar ola" is now "foo = [ fDirName bar ]" Install now always does a cp/chmod/etc, rather than using the system's install(1), which invariably seems broken. 3.3. Jam internal code changes $JAMUNAME is set on UNIX. (2.2.4). Jam ANSI-fied (2.3.0). jam.h now defines a bunch of symbols used by the other source files, so as minimize compiler- and platform-specific ifdefs. OSVER is no longer set by jam.h (it was only set for AIX). Jam does not depend on this variable at all, except to set $(OSFULL), which is used to determine jam's build directory. If the user needs to distinguish between various revs of OSs, he must set OSVER in the environment. 4. Fixed bugs Redefining a rule while it was executing could cause jam to crash. Reference counts are now used to prevent that, thanks to Matt Armstrong. Logic for computing chunk size when executing PIECEMEAL rules has been reworked to be a little more accurate, without danger of overflow, at the cost of being a little more compute intensive. Instead of computing an estimate chunksize in the (now gone) make1chunk(), make1cmds() now just goes full bore and tries to use all args. When that fails, it backs off by 10% of the source args until the command fits. It takes a little bit more compute time compared to the old logic, but when you're executing actions to build all of Shinola it's still pretty small in the scheme of things. The NT handle leak in execunix.c has been fixed, thanks to Gurusamy Sarathy. (2.2.1). 5. Porting Platforms newly supported or updated: AmigaOS (with gcc), courtesy of Alain Penders (2.2.2). Beos CYGWIN 1.1.4, courtesy of John Belmonte . IBM AS400 via Visual Age on NT (primitive) IBM OS/390 Unix System Services Linux SuSE on OS390 Linux Mips, ARM Lynx HPUX 11, IA64 Mac OS X Server, courtesy of Jeff_Sickel@sickel.com (2.2.5). Mac Rhapsody MPE IX 6.0 NetBSD QNX RTP (QNX 6.0) Siemens Sinix UNICOS VMS 6.2, 7.1 Windows NT IA64 5.1. NT Porting Notes Always create tmp .bat file for actions if JAMSHELL is set. That way, if JAMSHELL is a .bat file itself, it can handle single-command actions with more than 9 cmd line args. COMSPEC is no longer examined: cmd.exe is always used instead. Only cmd.exe can execute the Jambase rules anyhow. Jam can be built with Borland C++ 5.5. OS2 fixes: InstallBin now works. Filenames are now downshifted, so mixed case works better there, too. file_dirscan() can now scan the root ("c:\" or "\") directory, which it couldn't handle before. var_defines now ignores OS=Windows_NT, because it conflicts with Jam's setting of OS (to NT). 5.2. Mac OS 8/9 Notes The support for Mac is curious at best. It runs under MPW. It requires CodeWarrior Pro 5, but no longer requires GUSI. Use Build.mpw to bootstrap the build. The Mac specific definitions in the Jambase are not intended to be of general purpose, but are sufficient to have Jam build itself. =============================================================================== =============================================================================== Release Notes for Jam 2.2 1. Release info: Jam 2.2 October 22, 1997 VERSION 2.2 PATCHLEVEL 1 2. Compatibility Jam 2.2 is a roll-up of 'Jam - make(1) redux' release 2.1+. Most of the changes described below were available before this, in the jam.2.1.plus.tar ball. The Jam 2.2 language is a superset of the 2.1 language; Jamfiles, Jambase, and other rulesets used in 2.1 can be used with the 2.2 language support. See 'Jambase Changes', below, to see if your Jamfiles need any changes to work with the 2.2 Jambase. 3. Changes Since 2.1 New product name: Jam. (Executable program is still named 'jam'.) Documentation rewritten; HTML versions supplied. 3.1 Changes to Jam Language Rules may now have more fields than just $(<) and $(>). Local variables are now supported. The expression 'if $(A) in $(B)' is now supported. New variable modifiers :U and :L result in uppercased or lowercased values. New variable modifier :P reliably results in parent directory of either a file or directory. (Previously, :D was used, but on VMS :D of a directory name is just the directory name.) The :S variable modifier now results in the _last_ suffix if a filename has more than one dot (.) in it. New predefined $(JAMDATE) variable is initialized at runtime for simple date stamping. New predefined variables $(OSVER) and $(OSPLAT) are used to distinguish among operating system versions and hardware platforms, when possible. New 'bind' qualifier on action definitions allows variables other than $(<) and $(>) to be bound with SEARCH and LOCATE paths. Action buffer size is no longer limited by MAXCMD. Instead, each line in an action is limited by MAXLINE, defined for each OS, and the entire action size is limited by CMDBUF. 3.2 Jambase Changes (See Jamfile.html) Jambase has been reworked to incorporate new language features. A handful of new utility rules has been added: makeString, makeDirName, etc. New HDRGRIST variable in Jambase allows for headers with the same name to be distinguished. LOCATE_TARGET now has a new flavor, LOCATE_SOURCE, that is used by rules that generate source files (e.g., Yacc and Lex). Header file includes now happen in the proper order. The limit of 10 include files has been eliminated. The old "Install" rule is no longer available. Use InstallBin, InstallFile, InstallLib, InstallMan, or InstallShell instead. 3.3 'jam' Changes (See Jam.html) 'jam' can now be built as a stand-alone program, with Jambase compiled into the executable. An external or alternate Jambase can still be referenced explicitly with -f. On command failure, 'jam' now emits the text of the command that failed. This is a compromise between the normal -d1 behavior (where commands were never seen) and -d2 (where commands are always seen). 'jam' now exits non-zero if it doesn't have a total success. A parse error, sources that can't be found, and targets that can't be built all generate non-zero exit status. The debugging levels (-d flags) have been slightly redefined. The supplied Jamfile now builds 'jam' into a platform specific subdirectory. This lets you use the same source directory to build 'jam' for more than one platform. The supplied Jamfile does not rebuild generated source files by default. (They are supplied with the distribution.) See Jamfile for more information. 4. Fixed Bugs The 'include' bug has finally been fixed, so that include statements take effect exactly when they are executed, rather than after the current statement block. This also corrects the problem where an 'include' within an 'if' block would wind up including the file one token after the 'if' block's closing brace. Credit goes to Thomas Woods for suggesting that the parse tree generation and parse tree execution be paired in their own loop, rather than having the parser execute the tree directly. The setting and extracting of grist has been regularized: normally, if you set a component of a filename (using the :DBSMG= modifiers), you are supposed to include the delimiters that set off the component: that is, you say "$(x:S=.suffix)", including the ".". But with grist it was inconsistent between setting and getting: setting grist required no <>'s, while getting grist included them. Getting grist continues to return the <>'s, but now setting grist can either include them (the new way) or not (the old way). 'actions together' now suppresses duplicate sources from showing up in $(>). Accessing variables whose names contained ['s (as happens with MkDir on VMS) wasn't working, because it treated the [ as an array subscript. Now [ and ] are, like :, handled specially so that they can appear in variable values. The 'if' statement now compares all elements in expressions; previously, it only compared the first element of each list. If a command line in an action is longer than MAXLINE (formerly MAXCMD), 'jam' now issues an error and exits rather than dumping core. If a Jamfile ended without a trailing newline, jam dumped core. This has been fixed. 5. Porting See jam.h for the definitive list of supported platforms. Since 2.1, support has been added for: Macintosh MPW Alpha VMS Alpha NT NT PowerPC BeOS MVS OE UNIXWARE QNX SINIX (Nixdorf) OS/2 Interactive UNIX (ISC), courtesy of Matthew Newhook 5.1 NT Support Fixes The NT command executor now handles multiple line actions, by writing multi-line actions to a batch file and executing that. Targets are universally lowercased on NT. (Matthew Newhook) Concurrent process support is fully enabled for NT. (Gurusamy Sarathy ) Path handling: Jam now knows that the directory component of "D:\" is "D:\", just as on unix it knows that the directory component of "/" is "/". It also now successfully gets the timestamp for "D:\" or just plain "\". 5.2 VMS Support Fixes VMS support is much, much better now. The path name manipulation routines (in pathvms.c) were more or less rewritten, and they now handle the vagaries of combining directory and file names properly. Targets are universally lowercased on VMS. Multi-line command blocks on VMS are now executed in a single system() call rather than separate ones for each line, so that actions can be DCL scripts. =============================================================================== =============================================================================== Release notes for Jam 2.1. 1. Release info: Jam 2.1 February 1, 1996 VERSION 2.1 PATCHLEVEL 0 2. Porting Linux is now supported. FREEBSD is now supported. SCO ("M_XENIX") now supported. NCR now supported. NEXT support from karthy@dannug.dk (Karsten Thygesen) DECC support from zinser@axp614.gsi.de (Martin P.J. Zinser) I have changes for OS/2, but no way to test them. Volunteers? I have VMS multiprocess support, but no way to test it. Volunteers? 2.1. NT Support fixes. The NT support is considerably more real than it was in 2.0. Filent.c had its syntax error corrected, it no longer skips the first entry when scanning directories, and it handles string tables in archives (for long object file names). The Jambase was changed a bit to support the various C/C++ compilers on NT, although it has only been thorougly tested with MSVC20. You still need to set MSVCNT or BCCROOT to the root of the the compiler's directory tree, and you'll get an error if you don't set it (rather than getting a pile of mysterious errors). 2.2. Other porting fixes. SPLITPATH now set up for UNIX (:), NT (;), VMS (,) Jambase support for Solaris works better now: the location of AR is hardwired to /usr/ccs/bin/ar and it knowns "install" doesn't take -c. Solaris -- how the mighty have fallen. To handle Linux's wacko yacc, jamgram.h is now included after scan.h so that YYSTYPE is define. 3. Jambase Changes (see Jamfile.html) SubDir now computes the root directory for the source tree, if the variable naming the root directory isn't set in the environment. It counts the number of directory elements leading from the root to the current directory (as passed to SubDir) and uses that many "../"'s to identify the root. This means that to use SubDir you no longer have to have anything special set in the environment. InstallFile is now an alias for InstallLib. 'first' is now dependency of all pseudo-targets (all, files, exe, lib, shell), so that jamming any of these pseudo-targets also builds any dependencies of 'first'. The File rule definition in the Jambase was missing an &. The File rule now calls the Clean rule, so that installed files get cleaned. 4. Jam changes (see Jam.html) Variables may now be set on the command line with -svar=value. Targets marked with NOUPDATE are now immune to the -a (anyhow) flag. Previously, the MkDir rule would try to recreate directories that already exist when jam was invoked with -a. A new variable, $(JAMVERSION), joins the small list of built-in variables. It it set to the release of jam, currently "2.1". If an actions fails, jam now deletes the target(s). It won't delete libraries or other targets that are composites. This is now consistent with jam's behavior on interrupts (it deletes the targets). Jam had a nasty bug when setting multiple variables to the same value: if the first two variable names were the same, the variable value got trashed. This also affected "on target" variables if the first two targets were the same. For example: FOO on bar.c bar.c foo.c = a b c ; This would mangle the value of FOO for bar.c and foo.c. This has been fixed. Jam would generate bogus numbers when reporting the number of targets updated after an interrupt. It now is more careful about counting. The debugging flag -d has been extended. In addition to supporting -dx (turn on debugging for all levels up to x) there is also now -d+x (turn on debugging at only level x). The default output level is -d1 (-or d2 if -n is given); this can be turned off with -d0. The debug levels are listed in jam.1 and jam.h. The parsing debug output now uses indenting to indicate when one rule invokes another. =============================================================================== =============================================================================== Release notes for Jam 2.0. 1. Release info: Jam 2.0 March 10, 1994 VERSION 2.0 PATCHLEVEL 5 2. Porting Windows/NT is now (crudely) supported, courtesy of Brett Taylor and Laura Wingerd. COHERENT/386 is now supported, courtesy of Fred Smith. Solaris archive string table for long archive names is now supported, thanks to Mike Matrigali. 3. Compatibility Jam 2.0 syntax is a superset of Jam 1.0 syntax, and thus it can interpret a Jam 1.0 Jambase. The Jam 2.0 Jambase is a superset of the Jam 1.0 Jambase, and thus it can include a Jamfile written for Jam 1.0. 4. Changes from Jam 1.0 to Jam 2.0 4.1. Documentation changes New Jamfile.5 manual page, with lots of examples and easy reading. It replaces both the old "Examples" file as well as the old Jambase.5 manual page. jam.1 edited by Stephen W. Liddle and Diane Holt. 4.2. Jambase Changes (see Jamfile.5) 4.2.1. New rules: There are new rules to make handling subdirectories easier: SubDir, SubInclude, SubDirCcFlags, SubDirHdrs. There are new rules to handle file-specific CCFLAGS and HDRS: ObjectCcFlags and ObjectHdrs. Misc new rules: HardLink, InstallShell, MkDir. New rule "clean" that deletes exactly what jam has built, and "uninstall" that deletes exactly what was installed. New rules for handling suffixes .s, .f, .cc, .cpp, .C. 4.2.2. Old rules: The InstallBin, Lib, Man, and the new Shell rules now take the destination directory as the target and the files to be copied as sources. These rules formerly took the files to be copied as targets, and used built-in destination directories of $(BINDIR), $(LIBDIR), $(MANDIR), and $(BINDIR). The InstallBin, Lib, Man, and Shell rules use the install(1) program now, instead of doing their own copying. The Cc rule now uses -o when possible, rather than moving the result. Some platforms (Pyramid?) have a broken -o. Jambase rules taking libraries, objects, and executables now all ignore the suffixes provided and use the one defined in the Jambase for the platform. Stupid yyacc support moved out of Jambase, as jam is its only likely user. Jambase now purturbs library sources with a "grist" of SOURCE_GRIST. 4.2.3. Misc: The names of the default rules defined in Jambase have been lowercased and un-abbreviated, to be more imake(1) like. The Jambase has been reorganized and sorted, with VMS and NT support moved in from their own files. The Jambase has been relocated on UNIX from /usr/local/lib/jam to /usr/local/lib. 4.3. Jam changes (see jam.1) 4.3.1. Flags: New -a (anyhow) flag: means build everything. New -j flag: run jobs in parallel. Old -t now rebuilds the touched target, rather that just the target's parents. -n now implies -d2, so that you see what's happening. The debug level can be subsequently overridden. New -v to dump version. 4.3.2. Rules: New ALWAYS rule behaves like -t: always builds target. New EXIT rule makes it possible to raise a fatal error. New LEAVES rule which say target depends only on the update times of the leaf sources. New NOUPDATE rule says built targets only if they don't exist. NOTIME has been renamed NOTFILE, to more accurately reflect its meaning (it says a target is not to be bound to a file). 4.3.3. Variables: New special variable JAMSHELL: argv template for command execution shell. Variables, both normal and target-specific, can have their value appended with the syntax "var += value" or "var on target += value". "?=" is now synonymous with "default =". Imported enviroment variable values are now split at blanks (:'s if the variable name ends in PATH), so that they become proper list values. 4.3.4. Misc: Files to be sourced with "include" are now bound first, so $(SEARCH) and $(LOCATE) affect them. They still can't be built, though. New modifier on "actions": "existing" causes $(>) to expand only those files that currently exist. 4.3.5. Bug fixes: When scanning tokens known to be argument lists (such as the arguments to rule invocations and variable assignment), the parser now tells the scanner to ignore alphabetic keywords, as all such lists terminate with punctuation keywords (like : or ;). This way, alphabetic keywords don't need to be quoted when they appear as arguments. The scanner has been fixed to handle oversized tokens, unterminated quotes, unterminated action blocks, and tokens abutting EOF (i.e. a token with no white space before EOF). The progress report "...on xth target..." used to count all targets, rather than just those with updating actions. Since the original pronouncement of targets to be udpated included only those with updating actions, the progress report has been changed to match. 'If' conditionals now must be single arguments. Previously, they could be zero or more arguments, which didn't make much sense, and made things like 'foo == bar' true. The comparison operator is '=', and '==' just looked like the second of three arguments in the unary "non-empty argument list" conditional. Header files indirectly including themselves were mistakenly reported as being dependent on themselves. Recursing through header file dependencies is now done after determining the fate of the target. The variable expansion support was expanding $(X)$(UNDEF) as if it were $(X). It now expands to an empty list, like it should. The UNIX version of file_build() didn't handle "dir/.suffix" right. Now it does. The VMS command buffer was assumed to be as large as 1024 bytes, which isn't the case everywhere as it is related to some weird quota. It has been lowered to 256. $(>) and $(<) wouldn't expand in action blocks if the targets were marked with NOTIME. Now they expand properly. Malloc() return values are now checked. The variable expansion routine var_expand() is now a little faster, by taking a few often needed shortcuts. The VMS version of file_build() used the wrong length when re-rooting file names that already had directory compoents. This was fixed. Various tracing adjustments were made. 5. Limitations/Known Bugs The new Windows/NT support has only been marginally tested. It is dependent on certain variables being set depending on which compiler you are using. You'll need to look in the file Jambase and see what variables are expected to be set. The VMS support has been tested, courtesy of the DEC guest machine, but has not been hammered fully in release 2.0. It was used quite a bit in Jam 1.0. Jam clean when there is nothing to clean claims it is updating a target. Because the include statement works by pushing a new file in the input stream of the scanner rather than recursively invoking the parser on the new file, multiple include statements in a rule's procedure causes the files to be included in reverse order. If the include statement appears inside an if block, the parser's attempt to find the else will cause the text of the included file to appear after the first token following the statement block. This is rarely what is intended. In a rule's actions, only $(<) and $(>) refer to the bound file names: all other variable references get the unbound names. This is a pain for $(NEEDLIBS), because it means that library path can't be bound using $(SEARCH) and $(LOCATE). With the -j flag, errors from failed commands can get staggeringly mixed up. Also, because targets tend to get built in a quickest-first ordering, dependency information must be quite exact. Finally, beware of parallelizing commands that drop fixed-named files into the current directory, like yacc(1) does. A poorly set $(JAMSHELL) is likely to result in silent failure.