| =head1 NAME |
| |
| README.hints - hint files used by Configure |
| |
| =head1 DESCRIPTION |
| |
| These files are used by Configure to set things which Configure either |
| can't or doesn't guess properly. Most of these hint files have been |
| tested with at least some version of perl5, but some are still left |
| over from perl4. |
| |
| Please send any problems or suggested changes to perlbug@perl.org. |
| |
| =head1 Hint file naming convention. |
| |
| Each hint file name should have only |
| one '.'. (This is for portability to non-unix file systems.) Names |
| should also fit in <= 14 characters, for portability to older SVR3 |
| systems. File names are of the form $osname_$osvers.sh, with all '.' |
| changed to '_', and all characters (such as '/') that don't belong in |
| Unix filenames omitted. |
| |
| For example, consider Sun OS 4.1.3. Configure determines $osname=sunos |
| (all names are converted to lower case) and $osvers=4.1.3. Configure |
| will search for an appropriate hint file in the following order: |
| |
| sunos_4_1_3.sh |
| sunos_4_1.sh |
| sunos_4.sh |
| sunos.sh |
| |
| If you need to create a hint file, please try to use as general a name |
| as possible and include minor version differences inside case or test |
| statements. For example, for IRIX 6.X, we have the following hints |
| files: |
| |
| irix_6_0.sh |
| irix_6_1.sh |
| irix_6.sh |
| |
| That is, 6.0 and 6.1 have their own special hints, but 6.2, 6.3, and |
| up are all handled by the same irix_6.sh. That way, we don't have to |
| make a new hint file every time the IRIX O/S is upgraded. |
| |
| If you need to test for specific minor version differences in your |
| hints file, be sure to include a default choice. (See aix.sh for one |
| example.) That way, if you write a hint file for foonix 3.2, it might |
| still work without any changes when foonix 3.3 is released. |
| |
| Please also comment carefully on why the different hints are needed. |
| That way, a future version of Configure may be able to automatically |
| detect what is needed. |
| |
| A glossary of config.sh variables is in the file Porting/Glossary. |
| |
| =head1 Setting variables |
| |
| =head2 Optimizer |
| |
| If you want to set a variable, try to allow for Configure command-line |
| overrides. For example, suppose you think the default optimizer |
| setting to be -O2 for a particular platform. You should allow for |
| command line overrides with something like |
| |
| case "$optimize" in |
| '') optimize='-O2' ;; |
| esac |
| |
| or, if your system has a decent test(1) command, |
| |
| test -z "$optimize" && optimize='-O2' |
| |
| This allows the user to select a different optimization level, e.g. |
| -O6 or -g. |
| |
| =head2 Compiler and Linker flags |
| |
| If you want to set $ccflags or $ldflags, you should append to the existing |
| value to allow Configure command-line settings, e.g. use |
| |
| ccflags="$ccflags -DANOTHER_OPTION_I_NEED" |
| |
| so that the user can do something like |
| |
| sh Configure -Dccflags='FIX_NEGATIVE_ZERO' |
| |
| and have the FIX_NEGATIVE_ZERO value preserved by the hints file. |
| |
| =head2 Libraries |
| |
| Configure will attempt to use the libraries listed in the variable |
| $libswanted. If necessary, you should remove broken libraries from |
| that list, or add additional libraries to that list. You should |
| *not* simply set $libs -- that ignores the possibilities of local |
| variations. For example, a setting of libs='-lgdbm -lm -lc' would |
| fail if another user were to try to compile Perl on a system without |
| GDBM but with Berkeley DB. See hints/dec_osf.sh and hints/solaris_2.sh |
| for examples. |
| |
| =head2 Other |
| |
| In general, try to avoid hard-wiring something that Configure will |
| figure out anyway. Also try to allow for Configure command-line |
| overrides. |
| |
| =head1 Working around compiler bugs |
| |
| Occasionally, the root cause of a bug in perl turns out to be due to a bug |
| in the compiler. Often, changing the compilation options (particularly the |
| optimization level) can work around the bug. However, if you try to do |
| this on the command line, you will be changing the compilation options for |
| every component of perl, which can really hurt perl's performance. |
| Instead, consider placing a test case into the hints directory to detect |
| whether the compiler bug is present, and add logic to the hints file to |
| take a specific and appropriate action |
| |
| =head2 Test-case conventions |
| |
| Test cases should be named "tNNN.c", where NNN is the next unused sequence |
| number. The test case must be executable and should display a message |
| containing the word "fails" when the compiler bug is present. It should |
| display the word "works" with the compiler bug is not present. The test |
| cases should be liberally commented and may be used by any hints file that |
| needs them. See the first hints file (t001.c) for an example. |
| |
| =head2 Hint file processing |
| |
| The hint file must define a call-back unit (see below) that will compile, |
| link, and run the test case, and then check for the presence of the string |
| "fails" in the output. If it finds this string, it sets a special variable |
| to specify the compilation option(s) for the specific perl source file that |
| is affected by the bug. |
| |
| The special variable is named "XXX_cflags" where "XXX" is the name of |
| the source file (without the ".c" suffix). The value of this variable |
| is the string "optimize=YYY", where "YYY" is the compilation option |
| necessary to work around the bug. The default value of this variable |
| is "-O" (letter O), which specifies that the C compiler should compile |
| the source program at the default optimization level. If you can |
| avoid the compiler bug by disabling optimization, just reset the |
| "optimize" variable to the null string. Sometimes a bug is present at |
| a higher optimization level (say, O3) and not present at a lower |
| optimization level (say, O1). In this case, you should specify the |
| highest optimization level at which the bug is not present, so that |
| you will retain as many of the benefits of code optimization as |
| possible. |
| |
| For example, if the pp_pack.c source file must be compiled at |
| optimization level 0 to work around a problem on a particular |
| platform, one of the statements |
| |
| pp_pack_cflags="optimize=-O0" or |
| pp_pack_cflags="optimize=" |
| |
| will do the trick, since level 0 is equivalent to no optimization. |
| (In case your printer or display device does not distinguish the |
| letter O from the digit 0, that is the letter O followed by the digit |
| 0). You can specify any compiler option or set of options here, not |
| just optimizer options. These options are appended to the list of all |
| other compiler options, so you should be able to override almost any |
| compiler option prepared by Configure. (Obviously this depends on how |
| the compiler treats conflicting options, but most seem to go with the |
| last value specified on the command line). |
| |
| You should also allow for the XXX_cflags variable to be overridden on the |
| command line. |
| |
| See the vos.sh hints file for an extended example of these techniques. |
| |
| =head1 Hint file tricks |
| |
| =head2 Printing critical messages |
| |
| [This is still experimental] |
| |
| If you have a *REALLY* important message that the user ought to see at |
| the end of the Configure run, you can store it in the file |
| 'config.msg'. At the end of the Configure run, Configure will display |
| the contents of this file. Currently, the only place this is used is |
| in Configure itself to warn about the need to set LD_LIBRARY_PATH if |
| you are building a shared libperl.so. |
| |
| To use this feature, just do something like the following |
| |
| $cat <<EOM | $tee -a ../config.msg >&4 |
| |
| This is a really important message. Be sure to read it |
| before you type 'make'. |
| EOM |
| |
| This message will appear on the screen as the hint file is being |
| processed and again at the end of Configure. |
| |
| Please use this sparingly. |
| |
| =head2 Propagating variables to config.sh |
| |
| Sometimes, you want an extra variable to appear in config.sh. For |
| example, if your system can't compile toke.c with the optimizer on, |
| you can put |
| |
| toke_cflags='optimize=""' |
| |
| at the beginning of a line in your hints file. Configure will then |
| extract that variable and place it in your config.sh file. Later, |
| while compiling toke.c, the cflags shell script will eval $toke_cflags |
| and hence compile toke.c without optimization. |
| |
| Note that for this to work, the variable you want to propagate must |
| appear in the first column of the hint file. It is extracted by |
| Configure with a simple sed script, so beware that surrounding case |
| statements aren't any help. |
| |
| By contrast, if you don't want Configure to propagate your temporary |
| variable, simply indent it by a leading tab in your hint file. |
| |
| For example, prior to 5.002, a bug in scope.c led to perl crashing |
| when compiled with -O in AIX 4.1.1. The following "obvious" |
| workaround in hints/aix.sh wouldn't work as expected: |
| |
| case "$osvers" in |
| 4.1.1) |
| scope_cflags='optimize=""' |
| ;; |
| esac |
| |
| because Configure doesn't parse the surrounding 'case' statement, it |
| just blindly propagates any variable that starts in the first column. |
| For this particular case, that's probably harmless anyway. |
| |
| Three possible fixes are: |
| |
| =over |
| |
| =item 1 |
| |
| Create an aix_4_1_1.sh hint file that contains the scope_cflags |
| line and then sources the regular aix hints file for the rest of |
| the information. |
| |
| =item 2 |
| |
| Do the following trick: |
| |
| scope_cflags='case "$osvers" in 4.1*) optimize=" ";; esac' |
| |
| Now when $scope_cflags is eval'd by the cflags shell script, the |
| case statement is executed. Of course writing scripts to be eval'd is |
| tricky, especially if there is complex quoting. Or, |
| |
| =item 3 |
| |
| Write directly to Configure's temporary file UU/config.sh. |
| You can do this with |
| |
| case "$osvers" in |
| 4.1.1) |
| echo "scope_cflags='optimize=\"\"'" >> UU/config.sh |
| scope_cflags='optimize=""' |
| ;; |
| esac |
| |
| Note you have to both write the definition to the temporary |
| UU/config.sh file and set the variable to the appropriate value. |
| |
| This is sneaky, but it works. Still, if you need anything this |
| complex, perhaps you should create the separate hint file for |
| aix 4.1.1. |
| |
| =back |
| |
| =head2 Call-backs |
| |
| =over 4 |
| |
| =item Compiler-related flags |
| |
| The settings of some things, such as optimization flags, may depend on |
| the particular compiler used. For example, consider the following: |
| |
| case "$cc" in |
| *gcc*) ccflags="$ccflags -posix" |
| ldflags="$ldflags -posix" |
| ;; |
| *) ccflags="$ccflags -Xp -D_POSIX_SOURCE" |
| ldflags="$ldflags -Xp" |
| ;; |
| esac |
| |
| However, the hints file is processed before the user is asked which |
| compiler should be used. Thus in order for these hints to be useful, |
| the user must specify sh Configure -Dcc=gcc on the command line, as |
| advised by the INSTALL file. |
| |
| For versions of perl later than 5.004_61, this problem can |
| be circumvented by the use of "call-back units". That is, the hints |
| file can tuck this information away into a file UU/cc.cbu. Then, |
| after Configure prompts the user for the C compiler, it will load in |
| and run the UU/cc.cbu "call-back" unit. See hints/solaris_2.sh for an |
| example. Some callbacks exist for other variables than cc, such as for |
| uselongdouble. At the present time, these callbacks are only called if the |
| variable in question is defined; however, this may change, so the scheme in |
| hints/solaris_2.sh of checking to see if uselongdouble is defined is a good |
| idea. |
| |
| =item Call status |
| |
| Call-backs are only called always, even if the value for the call-back is |
| uset: UU/usethreads.cbu is called when Configure is about to deal with |
| threads. All created call-backs from hints should thus check the status |
| of the variable, and act upon it. |
| |
| =item Future status |
| |
| I hope this "call-back" scheme is simple enough to use but powerful |
| enough to deal with most situations. Still, there are certainly cases |
| where it's not enough. For example, for aix we actually change |
| compilers if we are using threads. |
| |
| I'd appreciate feedback on whether this is sufficiently general to be |
| helpful, or whether we ought to simply continue to require folks to |
| say things like "sh Configure -Dcc=gcc -Dusethreads" on the command line. |
| |
| =back |
| |
| Have the appropriate amount of fun :-) |
| |
| Andy Dougherty doughera@lafayette.edu (author) |
| Paul Green paul.green@stratus.com (compiler bugs) |