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diff --git a/erts/emulator/pcre/README.pcre_update.md b/erts/emulator/pcre/README.pcre_update.md new file mode 100644 index 0000000000..5f2414f0d9 --- /dev/null +++ b/erts/emulator/pcre/README.pcre_update.md @@ -0,0 +1,733 @@ +# How to update the PCRE version used by Erlang + +## The basic changes to the PCRE library + +To work with the Erlang VM, PCRE has been changed in two important ways: + +1. The main execution machine in pcre\_exec has been modified so that +matching can be interrupted and restarted. This functionality utilizes +the code that implements recursion by allocating explicit +"stack-frames" in heap space, which basically means that all local +variables in the loop are part of a struct which is kept in "malloced" +memory on the heap and there are no real stack variables that need to +be pushed on the C stack in the case of recursive calls. This is a +technique we also use inside the VM to avoid building large C +stacks. In PCRE this is enabled by the NO\_RECURSE define, so that is a +prerequisite for the ERLANG\_INTEGRATION define which also adds labels +at restart points and counts "reductions". + +2. All visible symbols in PCRE gets the erts_ prefix, so that NIF's +and such using a "real" pcre library does not get confused (or 're' +gets confused when a "real" pcre library get's loaded into the VM +process). + +3. All irrelevant functionality has been stripped from the library, +which means for example UTF16 support, jit, DFA execution +etc. Basically the source files handling this are removed, together +with any build support from the PCRE project. We have our own +makefiles etc. + +## Setting up an environment for the work + +I work with four temporary directories when doing this (the examples +are from the updating of pcre-7.6 to pcre-8.33); + + ~/tmp/pcre> ls + epcre-7.6 epcre-8.33 pcre-7.6 pcre-8.33 + +I've unpacked the plain pcre sources in pcre-* and will work with our +patched sources in the epcre-* directories. + +Make sure your ERL_TOP contains a *built* version of Erlang (and you have made a branch) + +First unpack the pcre libraries (which will create the pcre-* +directories) and then copy our code to the old epcre directory: + + ~/tmp/pcre> tar jxf $ERL_TOP/erts/emulator/pcre/pcre-7.6.tar.bz2 + ~/tmp/pcre> tar jxf ~/Downloads/pcre-8.33.tar.bz2 + ~/tmp/pcre> mkdir epcre-7.6 epcre-8.33 + ~/tmp/pcre> cd epcre-7.6/ + ~/tmp/pcre/epcre-7.6> cp -r $ERL_TOP/erts/emulator/pcre/* . + ~/tmp/pcre/epcre-7.6> rm pcre-7.6.tar.bz2 + +Leave the obj directory, you may need the libepcre.a file... + +If you find it easier, you can revert the commit in GIT that adds the +erts_ prefix to the previous version before continuing work, but as +that is a quite small diff in newer versions of PCRE, it is probably +not worth it. Still, you will find the erts_ prefix being a separate +commit when integrating 8.33, so if you're nice, you will do the same +for the person coming after you... + +## Generating a diff for our changes to PCRE + +Before you generate a diff (that, in an ideal world, would be used to +automatically patch the newer version of pcre, which will probably +only work for minor PCRE updates), we need to configure the old pcre. + + ~/tmp/pcre/epcre-7.6> cd ../pcre-7.6 + ~/tmp/pcre/pcre-7.6> ./configure --enable-utf8 --enable-unicode-properties --disable-shared --disable-stack-for-recursion + +Note that for newer versions, the configure flag '--enable-utf8' +should be replaced with '--enable-utf' + +So we now generate a diff: + + ~/tmp/pcre/pcre-7.6> cd ../epcre-7.6 + ~/tmp/pcre/epcre-7.6> (for x in *.[ch]; do if [ -f ../pcre-7.6/$x ]; then diff -c ../pcre-7.6/$x $x; fi; done ) > ../epcre-7.6_clean.diff + +### What the diff means + +Let's now walk through the relevant parts of the diff. Some of the +differences might come from patches that probably are already in the +new version, For example in out 7.6, we had a security patch which +added the define WORK_SIZE_CHECK and used it in some places. Those can +probably safely be ignored, but to be on the safe side, check what's +already integrated in the new version. + +The interesting part is in pcre_exec.c. You will see things like + + #ifdef ERLANG_INTEGRATION + ... + #endif + +or + + #if defined(ERLANG_INTEGRATION) + ... + #endif + +and a lot of + + COST_CHK(1); + +or + + COST(min); + +and + + /* LOOP_COUNT: Ok */ + /* LOOP_COUNT: CHK */ + /* LOOP_COUNT: COST */ + + +scattered over the main loop. Those mean the following: + +* COST(int x) - consume reductions proportional to the integer + parameter, but no need for interruption here (it's like + bump_reductions without trapping). The loop they apply to also has a + 'LOOP_COUNT: COST' comment at it's head. + +* COST\_CHK(int x) - like COST(x), but also check that the reduction +counter does not reach zero. If it does, leave the execution loop to +be restarted at a later point. No real stack variables can be live +here. Note that variables like 'max' and 'min' are *not* real stack +variables, the NO\_RECURSION setting has taken care of that. 'i' is a +stack variable that's explicitly saved when trapping, so that will +also be correct when returning from a trap. So will 'c', 'rrc' and +flags like 'utf8', 'minimize' and 'posessive'. Those can also be +regarded as "non C-stack variables". The loop where they reside also +has a 'LOOP\_COUNT: CHK' comment. + +* /* LOOP_COUNT: Ok */ - means that I have checked the loop and it + only runs a deterministic set of iterations regardless of input, or + it has a call to RRECURSE in it's body, why we need not add more + cost than the normal reduction counting that will occur for each + instruction demands. + +The thing is that each loop in the function 'match' should be marked +with one of these comments. If no comment is present after you patched +the new release (if you successfully manage to do it automatically), +it may be a new regexp instruction that is added since the last +release. + +You will need to manually go through the main 'match' loop after +upgrading to verify that there are no unhandled loops in the regexp +machine loop (!). + +The COST\_CHK macro works like this: + +1. Add to the loop count. +2. If loop count > limit: + 1. Store the line (+100) in the Xwhere member of the frame structure + 2. Goto LOOP\_COUNT\_BREAK, which ultimately returns from the function +3. Insert a label, which is named L\_LOOP\_COUNT\_<line number> + +LOOP\_COUNT\_BREAK code will create an extra "stack frame" on the heap +allocated stack used if NO\_RECURSION is set, and will store the few +locals that are not already in the ordinary stack frame there (like +'c' and 'i'). + +When we continue execution (after a trap up to the main Erlang +scheduler), we will jump to LOOP\_COUNT\_RETURN, which will restore +the local variables and will jump to the labels. The jump code looks +like this in the C source: + + switch (frame->Xwhere) + { + #include "pcre_exec_loop_break_cases.inc" + default: + DPRINTF(("jump error in pcre match: label %d non-existent\n", frame->Xwhere)); + return PCRE_ERROR_INTERNAL; + } + +When building, pcre\_exec\_loop\_break\_cases.inc will be generated +during build by pcre.mk, it will look like: + + case 791: goto L_LOOP_COUNT_691; + case 1892: goto L_LOOP_COUNT_1792; + case 1999: goto L_LOOP_COUNT_1899; + +etc + +So, simply put, all C-stack variables are saved when we have consumed +our reductions, we return from the function and, as there is no real +recursion we immediately fall out into the re:run BIF, which with the +help of a magic binary keeps track of the heap allocated stack for the +regexp machine. When we return from trapping out to the scheduler, all +vital data is restored and we continue from exactly the same state as +we left. What's needed is to patch this into the new pcre_exec and +check all new instructions to determine what might need updating in +terms of COST, COST\_CHK etc. + +Well, that's *almost* everything, because there is of course more... + +The actual interface function, 'pcre\_exec', needs the same treatment +as the actual regexp machine loop, that is we need to store all local +variables between restarts. Unfortunately the NO\_RECURSE setting does +not do this, we need to do it ourselves. So there's quite a diff in +that function too, where a big struct is declared, containing every +local variable in that function, together with either local copies +that are swapped in and out, or macros that directly access the heap +allocated struct. The struct is called `PcreExecContext`. + +If a context is present, we are restarting and therefore restore +everything. If we are restarting we can also skip all initialization +code in the function and jump more or less directly to the +RESTART_INTERRUPTED label and the call to 'match', which is the actual +regexp machine loop. + +There are a few places in the pcre_exec we need to do some housekeeping, you will see code like: + + if ((extra_data->flags & PCRE_EXTRA_LOOP_LIMIT) != 0) + { + *extra_data->loop_counter_return = + (extra_data->loop_limit - md->loop_limit); + } + +Make sure, after updating, that this housekeeping is done whenever we +do not reach the call to 'match'. + +So, now we in theory know what to do, so let's do it: + +But... + +## File changes in the new version of PCRE + +First we need to go through what's changed in the new library +version. Files may have new names, functions may have moved and so on. + +Start by building the new library: + + ~/tmp/pcre> cd pcre-8.33/ + ~/tmp/pcre/pcre-8.33> ./configure --enable-utf --enable-unicode-properties --disable-shared --disable-stack-for-recursion + ~/tmp/pcre/pcre-8.33> make + +In the make process, you will probably notice most files that are +used, but you can bet that's not all not all... + +To begin with you will need a default table for Latin-1 characters, so: + + ~/tmp/pcre/pcre-8.33> cc -DHAVE_CONFIG_H -o dftables dftables.c + ~/tmp/pcre/pcre-8.33> LANG=sv_SE ./dftables -L ../epcre-8.33/pcre_latin_1_table.c + +Compare it to the pcre\_latin\_1\_table.c in the old version, they +should not differ in any significant way. + +A good starting point is then to try to find all files in the new +version of the library that have (probably) the same names as the +one's in our distribution: + + ~/tmp/pcre/pcre-8.33> cd ../epcre-7.6/ + ~/tmp/pcre/epcre-7.6> for x in *.[ch]; do if [ '!' -f ../pcre-8.33/$x ]; then echo $x; else cp ../pcre-8.33/$x ../epcre-8.33/; fi; done + +This will output a list of files not found in the new distro. Let's +look at the list from the example upgrade: + + local_config.h + make_latin1_table.c + pcre_info.c + pcre_latin_1_table.c + pcre_make_latin1_default.c + pcre_try_flipped.c + pcre_ucp_searchfuncs.c + ucpinternal.h + ucptable.h + +* local\_config.h - OK, that's our child, it contains PCRE-specific + configure-results (i.e. the #defines that are results from out + parameters to configure, like NO\_RECURSE etc). Just copy it and + edit it according to what specific settings you can find in the + generated config.h from the real library build. In our example case, + the #define SUPPORT\_UTF8 should be renamed to #define SUPPORT\_UTF + and #define VERSION "7.6" should be changed to #define VERSION + "8.33"... + +* make\_latin1\_table.c - it was renamed to dftables.c, so we copy + that instead. + +* pcre\_info.c - It was simply removed from the library. Good, because + it was useless... So just ignore. + +* pcre\_latin\_1\_table.c - No problem, we generated a new one in the + earlier stage. + +* pcre\_make\_latin1\_default.c - No longer used, a hack that's not + needed with dftables. Ignored + +* pcre\_try\_flipped.c - This functionality has been removed from + pcre\_exec, you cannot compile on one endianess and execute on + another any more :( Ignored. + +* pcre\_ucp\_searchfuncs.c, ucpinternal.h, ucptable.h - this + functionality is moved to pcre\_ucd.c, copy that one instead. + +OK, now go the other way and look at what was actually built for the new version of pcre: + + ~/tmp/pcre/epcre-7.6> cd ../pcre-8.33/ + ~/tmp/pcre/pcre-8.33> nm ./.libs/libpcre.a | egrep 'lib.*.o:' + +The output for this release was: + + libpcre_la-pcre_byte_order.o: + libpcre_la-pcre_compile.o: + libpcre_la-pcre_config.o: + libpcre_la-pcre_dfa_exec.o: + libpcre_la-pcre_exec.o: + libpcre_la-pcre_fullinfo.o: + libpcre_la-pcre_get.o: + libpcre_la-pcre_globals.o: + libpcre_la-pcre_jit_compile.o: + libpcre_la-pcre_maketables.o: + libpcre_la-pcre_newline.o: + libpcre_la-pcre_ord2utf8.o: + libpcre_la-pcre_refcount.o: + libpcre_la-pcre_string_utils.o: + libpcre_la-pcre_study.o: + libpcre_la-pcre_tables.o: + libpcre_la-pcre_ucd.o: + libpcre_la-pcre_valid_utf8.o: + libpcre_la-pcre_version.o: + libpcre_la-pcre_xclass.o: + libpcre_la-pcre_chartables.o: + +Libtool has changed the object names, but we can fix that and see what +sources we have already decided should exist: + + ~/tmp/pcre/pcre-8.33> NAMES=`nm ./.libs/libpcre.a | egrep 'lib.*.o:'| sed 's,libpcre_la-,,' | sed 's,.o:$,,'` + ~/tmp/pcre/pcre-8.33> for x in $NAMES; do if [ '!' -f ../epcre-8.33/$x.c ]; then echo $x; fi; done + +And the list contained: + + pcre_byte_order + pcre_jit_compile + pcre_string_utils + +pcre\_jit\_compile is actually needed, even though we have not enabled +jit, and the other two contain functionality needed, so just copy the +sources... + + ~/tmp/pcre/pcre-8.33> for x in $NAMES; do if [ '!' -f ../epcre-8.33/$x.c ]; then cp $x.c ../epcre-8.33/; fi; done + +## Test build of stripped down version of new PCRE + +Time to do a test build. Copy and edit the pcre.mk makefile and try to +get something that builds... + +I made a wrapper Makefile, hacked pcre.mk a little and did a few +changes to a few files, namely added: + + #ifdef ERLANG_INTEGRATION + #include "local_config.h" + #endif + +to pcre\_config.c and pcre\_internal.h. Also pcre.mk needs to get the +new files added and the old files removed, directory names need to be +changed and the wrapper can define most. My wrapper Makefile looked +like this: + + EPCRE_LIB = ./obj/libepcre.a + PCRE_GENINC = ./pcre_exec_loop_break_cases.inc + PCRE_OBJDIR = ./obj + V_AR = ar + V_CC = gcc + CFLAGS = -g -O2 -DHAVE_CONFIG_H -I/ldisk/pan/git/otp/erts/x86_64-unknown-linux-gnu + gen_verbose = + PCRE_DIR=. + include pcre.mk + +And the according variables were removed together with dependencies +from pcre.mk. Note that you will need to put things back in order in +pcre.mk after all testing is done. Once a 'make' is successful, you +can generate new dependencies: + + ~/tmp/pcre/epcre-8.33> gcc -MM -c -g -O2 -DHAVE_CONFIG_H -I/ldisk/pan/git/otp/erts/x86_64-unknown-linux-gnu -DERLANG_INTEGRATION *.c | grep -v $ERL_TOP + +Well, then you have to add $(PCRE\_OBJDIR)/ to each object and +$(PCRE\_DIR)/ to each header. I did it manually, it's just a couple of +files. Now your pcre.mk is fairly up to date and it's time to start +patching in the changes... + +## Actually patching in the changes to the C code + +### Fixing the functionality (interruptable pcre\_run etc) + +Begin with only pcre\_exec.c, that's the important part: + + ~/tmp/pcre/epcre-8.33> cd ../epcre-7.6/ + ~/tmp/pcre/epcre-7.6> diff -c ../pcre-7.6/pcre_exec.c ./pcre_exec.c > ../epcre_exec.c_7.6.diff + ~/tmp/pcre/epcre-7.6> cd ../epcre-8.33 + +Now - if you are lucky, you can patch the new pcre\_exec with the +patch command from the diff, but that may not be the case... Even if: + + ~/tmp/pcre/epcre-8.33> patch -p0 < ../epcre_exec.c_7.6.diff + +works like a charm, you still have to go through the main loop and see +that all do, while and for loops in the code contains COST\_CHK or at +least COST, or, if it's a small loop (over, say one UTF character), +mark it as OK with a comment. + +You should also check for other changes, like new local variables in +the pcre\_exec code etc. + +What will probably happen, is that the majority of chunks +fail. pcre\_exec is the main file for PCRE, one that is constantly +optimized and where every new feature ends up. You will probably see +so many failed HUNK's that you feel like giving up, but do not +despair, it's just a matter of patience and hard work: + +* First, fix the 'pcre\_exec' function. + + * Change the struct PcreExecContext to reflect the local variables + in this version of the code. + + * Add/update the defines that makes local variables in the code + actually stay in an allocated "exec\_context" and be sure to + initialize the "pseudo-stack-variables" in the same way as in + the declarations for the original version of the code. + + * The macros SWAPIN and SWAPOUT should be for variables that are + used a lot and we do not want to always access through the + struct. Also a few parameters are saved by SWAPIN and SWAPOUT. + + * What might be tricky is to get things deallocated in a proper + way, there is a function that's called from the BIF code to + clean up an exec\_context, be especially observant about how the + stack in the 'match' function is allocated! The first frame is + supposed to be on the C stack, but in our case is allocated in + the exec\_context. The rest of the frames are allocated but + never freed, not until the match is done. + + The variable 'frame' in the 'match' function is stored in our + additional field of the 'md' structure, that is the stack top, + but not necessarily the uppermost frame (due to reuse of old + frames, which is supposed to be an optimization...). + + * The housekeeping of the "reduction counter" in the extra\_data + struct needs to be added to all places where we break out of the + main loop of pcre\_exec. Look for 'break' and you will see the + places. Make sure to update + '*extra\_data->loop\_counter\_return' whenever you leave this + function. It all boils down to some code that loops over the + call for match and returns PCRE\_ERROR\_LOOP\_LIMIT and get's + jumped back to when the BIF is restarted. You will see it in + your diff and you will find a similar place in the new version + where you put basically the same code. + + * Fixing pcre\_exec takes about an hour of concentrated work, it + could be worse... + +* Next, go for the match function. It's simpler in some ways but + harder in other. The elimination of the C stack is already there, + you just need to modify it a little: + + * In the RRETURN macro for NO\_RECURSE, add updating of + md->loop\_limit before returning. You can see how it's done in + the diff. + + * RMATCH can be left as it is, at least it could in earlier + versions. Note however that you should mimic the allocation + strategies of RMATCH and RRETURN in the code at another place + later... The principle of the labels HEAP\_RECURSE and + HEAP\_RETURN are mimicked by our code in LOOP\_COUNT\_BREAK and + LOOP\_COUNT\_RETURN. You'll see later... + + * COST and COST\_CHK, together with the jump to + LOOP\_COUNT\_RETURN label are in the beginning of the function + 'match'. It's a block of macros and declaration of our local + variables loop\_count and loop\_limit. We patch in the code for + that, but may need to adopt it to new variable names etc. It's + important to handle the 'frames' variable correctly, dig it out + of the 'md' struct when we are restarting, but initialize it as + is done in normal NO\_RECURSE code otherwise. Note that the + COST\_CHK macro reuses the Xwhere field of the frame struct, it + is not needed when trapping. + + * The LOOP\_COUNT\_BREAK and the LOOP\_COUNT\_RETURN code can now + be added. Make sure to check both how a new stack frame should be + properly allocated by mimicking the code in RMATCH, and how (if) + it should be freed by mimicking RRETURN. Also check which + variables need to be saved. They are properly pointed out in + 8.33 with the comment 'These variables do not need to be + preserved over recursion' and appear in the beginning of the + function. Find variables of similar type in the frame structure + and reuse them. In 8.33 there are eight such variables. They are + placed at the end of the function 'match'. If You are reading + the diff, you need to scroll past all the COST\_CHK calls, + i.e. past the whole regexp machine loop. + + * Now take the time to add things like debug macros to the top of + the file and one single COST\_CHK (preferably the one right + after for(;;) in 'match'), and see if you can compile. You will + probably need to add some fields in the structures in pcre.h, + see from a larger diff what you need there and iterate until you + can compile. + + * So, what's left is to add all the COST and COST\_CHK macros, + plus marking all harmless loops as OK. There are a few rules + here: + + * Mark *every* loop with the comment 'LOOP\_COUNT: xxxx', + where xxxx is either 'Ok', 'COST' or 'CHK'. There are 175 + 'LOOP\_COUNT:' comments in 8.33. + + * Loops marked 'Ok' need no macro, either because they are so + short (like over an UTF character) or because they contain + an RMATCH macro, in which case they will be accounted for + anyway. + + * Loops marked 'COST' will have an associated 'COST(N)' macro, + either before, if we know the amount of iterations, or + within. Reductions are counted, but we will not + interrupt. This is typically in what is expected to be + medium long loops or at places where interruption is hard + (like where we have local variables that are alive. The + selection between 'COST' and 'COST\_CHK' is hard. 'COST' is + much cheaper and usually enough, but when in doubt about the + loop length, try to use 'COST\_CHK', while making very sure + there are no live block-local variables that need to be + saved over the trap. There are 49 'COST' macros in 8.33. + + * Loops marked 'CHK' shall contain a 'COST\_CHK(N)' + macro. This macro both counts reductions and may result in + an interrupt and a return to Erlang space. It is expensive + and it is vital to ensure that there are no unexpected local + variables that live past the macro. Most variables are in + the pseudo stack frame, but some regexp instructions declare + temporaries inside blocks. Make sure they are not expected + to be alive after a COST\_CHK if they are not in the + 'heapframe' structure. If they are, you need to + conditionally move them to the 'heapframe' #if + defined(ERLANG\_INTEGRATION). in 8.33 the variables 'lgb' + and 'rgb' are preserved in this way. There are 54 + 'COST\_CHK's in 8.33. + + * I've marked a few block-local variables with warnings, but + look thoroughly through the main loop to detect any new + ones. + + * Be careful when it comes to freeing the context from Erlang + (the function erts\_pcre\_free\_restart\_data), Whatever is + done there has to work *both* when the context is freed in + the middle of an operation (because of trapping) and when + some things have been freed by a successful + return. Specifically, make sure to set md->offset\_vector to + NULL whenever it's freed (in the rest of the code) and + construct release\_match\_heapframes so that it can be + called multiple times for the same heapframe (set the next + pointer in the "static" frame, i.e. the one allocated in the + md to NULL after freeing). + + * To add the costs to the main loop takes less than one work day, + keep calm and continue... + +OK, now you are done with the pcre\_exec (or at least, you think +so). The rest is simpler. You have probably already handled 'pcre.h' +and 'pcre\_internal.h' to add fields to the structures etc. Looking at +a diff from an earlier version, you will see what's left. In upgrading +to 8.33, the following things was left to do after pcre\_exec was +fixed, remember you could generate a diff with: + + ~/tmp/pcre/epcre-8.33> cd ../epcre-7.6/ + ~/tmp/pcre/epcre-7.6> (for x in *.[ch]; do if [ -f ../pcre-7.6/$x ]; then diff -c ../pcre-7.6/$x $x; fi; done) > ../epcre-7.6.diff + +Open the diff in your favorite editor and remove whatever changes you +have already made, like everything that has to do with pcre\_exec.c +and probably a large part of pcre.h/pcre\_internal.h. + +The expected result is a diff that either contains only the +'%ExternalCopyright%' comments or contains them and the addition of +the erts\_ prefix, depending on if you reverted the prefix change +(using 'git revert') before starting to work. With a little luck, the +patch of the remaining stuff should be possible to apply +automatically. If anything fails, just add it manually. + +### Fixing the erts\_prefix + +The erts\_ prefix is mostly implemented by adding '#if +defined(ERLANG\_INTEGRATION)' to a lot of function headers, inside the +COMPILE\_UTF8 part. If you then also change the PRIV and PUBL macros +in pcre\_internal.h. Typical diffs look like: + + #if defined COMPILE_PCRE8 + + #if defined(ERLANG_INTEGRATION) + + #ifndef PUBL + + #define PUBL(name) erts_pcre_##name + + #endif + + #ifndef PRIV + + #define PRIV(name) _erts_pcre_##name + + #endif + + #else + #ifndef PUBL + #define PUBL(name) pcre_##name + #endif + #ifndef PRIV + #define PRIV(name) _pcre_##name + #endif + + #endif + +and + + #if defined COMPILE_PCRE8 + + #if defined(ERLANG_INTEGRATION) + + PCRE_EXP_DECL int erts_pcre_pattern_to_host_byte_order(pcre *argument_re, + + erts_pcre_extra *extra_data, const unsigned char *tables) + + #else + PCRE_EXP_DECL int pcre_pattern_to_host_byte_order(pcre *argument_re, + pcre_extra *extra_data, const unsigned char *tables) + + #endif + +Note that some data types, like pcre\_extra are accessed with the PUBL +macro, so they need to explicitly get the prefix added. pcre.h is a +pig, as it declares prototypes for all functions regardless of +compilation ode, so there is quite a lot of '#if +defined(ERLANG\_INTEGRATION)' to add there. + +Anyway, now try to patch, using a diff where you have removed the +changes you made manually (probably to pcre\_exec.c) but make sure to +save your work (temporary git repository?) before, so you can revert +any disasters... + + ~/tmp/pcre/epcre-7.6> cd ../epcre-8.33/ + ~/tmp/pcre/epcre-8.33> patch -p0 < ../epcre-7.6_clean2.diff + +Some hunks may certainly still fail, read through the .rej file and fix it. + +### ExternalCopyright + +Now you should check that the 'ExternalCopyright' comment is present +in all source files: + + ~/tmp/pcre/epcre-8.33> for x in *.[ch]; do if grep ExternalCopyright $x > /dev/null; then true; else echo $x; fi; done + +In this upgrade (from 7.6 to 8.33) we certainly had some new and +renamed files: + + dftables.c + pcre_byte_order.c + pcre_chartables.c + pcre_jit_compile.c + pcre_latin_1_table.c + pcre_string_utils.c + pcre_ucd.c + +Go through them manually and add the 'ExternalCopyright' comment. + +## Integrate with Erlang + +Now you are done with most of the tedious work. It's time to move this +into your branch of the Erlang source tree, remove old files and add +new ones, plus add the tar file with the original pcre dist. Remember +to fix your hacked version of pcre.mk and then try to build +Erlang. You might need to update 'erl\_bif\_re.c' to reflect any +changes in the PCRE library. When it builds, run the test suites. + +Make sure to rename any files that has new names and remove any files +that are no longer present before copying in the new versions from +your temporary directory. In our example we remove 'pcre\_info.c', +'pcre\_make\_latin1\_default.c', 'pcre\_try\_flipped.c', +'ucpinternal.h' and 'ucptable.h'. We rename 'make\_latin1\_table.c' to +'dftables.c' and 'pcre\_ucp\_searchfuncs.c' to 'pcre\_ucd.c'. + +After copying in the sources, we can try to build. Do not forget to +fix whatever you did in pcre.mk to make it build locally. + +## Update test suites + +The next step is to integrate the updated PCRE tests into our test suites. + +Copy testoutput[1-9] from the testdata directory of your new version +of pcre, to the re\_SUITE\_data in stdlib's test suites. Run the +test suites and remove any bugs. Usually the bugs come from the fact +that the PCRE test suites get better and from our implementation of +global matching, which may have bugs outside of the PCRE library. The +test suite 'pcre' is the one that runs these tests. Also copy +testoutput11-8 to testoutput10, the testoutput10 file in pcre is +nowadays for the DFA, which we do not use. + +The next step is to regenerate re\_testoutput1\_replacement\_test. How +to do that is in a comment in the beginning of the file. The key +module is run\_pcre\_tests.erl, which both driver the pcre test and +generate re\_testoutput1\_replacement\_test.erl. Watch during the +generation that you do not get to many of the "Fishy character" +messages, if they are more than, say 20, you will probably need to +address the UTF8 issues in the Perl execution. As it is now, we skip +non latin1 characters in this test. You will need to run iconv on the +generated module to make it UTF-8 before running tests. + +The exact same procedure goes for the re\_testoutput1\_split\_test.erl. + +Also add copyright headers to the files after converting them to UTF-8. + +After ironing out the rest of the bugs, you should be done with the +code. + +## Update documentation + +Now it's time for the documentation, which is fairly +straightforward. Diff the pcrepattern man pages from the old and new +PCRE distros and update the re.xml file accordingly. It may help to +have the generated HTML file from the new version to cut and paste +from, but as you will notice, it's quite a few changes from HTML to +XML. All lists are reformatted, the <pre> tags are made into +either <code> or <quite> etc. Also the <P> tags are +converted to lowercase and all mentioned options and function calls +are converted to their Erlang counterpart. Really awesome work that +requires thorough reading of all new text. For the upgrade from 7.6 +to 8.33, the update of the pcrepattern part of our manual page took +about eight hours. + +## Add new relevant options to re + +Then, when all this is done, you should add any new relevant options +from the PCRE library to both the code (erl\_bif\_re.c), the specs and +the Erlang function 'copt/1' (re.erl) and the manual page +(re.xml). Make sure the options are really relevant to add to the +Erlang API, check if they are compile or run-time options (or both) and +add them to the 'parse\_options' function of erl\_bif\_re.c. Adding an +option that is just passed through to PCRE is pretty simple, at least +"code wise". + +Now you are done. Run all test suites on all machines and you will be happy. + +## Final notes + +To avoid the work of a major upgrade, it is probably worth it to keep +in pace with the changes to PCRE. The upgrade from 7.6 to 8.33, +including tracking down bugs etc, took me a total of two weeks. If +smaller diffs from the PCRE development were integrated in a more +incremental fashion, it will be much easier each time and you will +have the PCRE library up to date. PCRE should probably be updated for +each major release, instead of every five years...
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