Detect and warn when pcre2test is linked with an alien POSIX library.

ChangeLog

@@ -42,6 +42,18 @@ instead of later. Previously the pre-scan carried on and could give a
 misleading incorrect error message. For example, /(?J)(?'a'))(?'a')/ gave a
 message about invalid duplicate group names.
 
+10. It has happened that pcre2test was accidentally linked with another POSIX
+regex library instead of libpcre2-posix. In this situation, a call to regcomp()
+(in the other library) may succeed, returning zero, but of course putting its
+own data into the regex_t block. In one example the re_pcre2_code field was
+left as NULL, which made pcre2test think it had not got a compiled POSIX regex,
+so it treated the next line as another pattern line, resulting in a confusing
+error message. A check has been added to pcre2test to see if the data returned 
+from a successful call of regcomp() are valid for PCRE2's regcomp(). If they 
+are not, an error message is output and the pcre2test run is abandoned. The 
+message points out the possibility of a mis-linking. Hopefully this will avoid 
+some head-scratching the next time this happens.
+
 
 Version 10.21 12-January-2016
 -----------------------------

src/pcre2posix.c

@@ -209,7 +209,7 @@ if ((cflags & REG_UTF) != 0)      options |= PCRE2_UTF;
 if ((cflags & REG_UCP) != 0)      options |= PCRE2_UCP;
 if ((cflags & REG_UNGREEDY) != 0) options |= PCRE2_UNGREEDY;
 
-preg->cflags = cflags;
+preg->re_cflags = cflags;
 preg->re_pcre2_code = pcre2_compile((PCRE2_SPTR)pattern, PCRE2_ZERO_TERMINATED,
    options, &errorcode, &erroffset, NULL);
 preg->re_erroffset = erroffset;
@@ -275,7 +275,7 @@ if ((eflags & REG_NOTEMPTY) != 0) options |= PCRE2_NOTEMPTY;
 put captured strings, ensure that nmatch is zero. This will stop any attempt to
 write to pmatch. */
 
-if ((preg->cflags & REG_NOSUB) != 0 || pmatch == NULL) nmatch = 0;
+if ((preg->re_cflags & REG_NOSUB) != 0 || pmatch == NULL) nmatch = 0;
 
 /* REG_STARTEND is a BSD extension, to allow for non-NUL-terminated strings.
 The man page from OS X says "REG_STARTEND affects only the location of the

src/pcre2posix.h

@@ -98,7 +98,7 @@ typedef struct {
   void *re_match_data;
   size_t re_nsub;
   size_t re_erroffset;
-  int cflags;
+  int re_cflags;
 } regex_t;
 
 /* The structure in which a captured offset is returned. */

src/pcre2test.c

@@ -4701,8 +4701,7 @@ if ((pat_patctl.control & CTL_POSIX) != 0)
 
   if (msg[0] == 0) fprintf(outfile, "\n");
 
-  /* Translate PCRE2 options to POSIX options and then compile. On success, set
+  /* Translate PCRE2 options to POSIX options and then compile. */
-  up a match_data block to be used for all matches. */
 
   if (utf) cflags |= REG_UTF;
   if ((pat_patctl.control & CTL_POSIX_NOSUB) != 0) cflags |= REG_NOSUB;
@@ -4713,7 +4712,10 @@ if ((pat_patctl.control & CTL_POSIX) != 0)
   if ((pat_patctl.options & PCRE2_UNGREEDY) != 0) cflags |= REG_UNGREEDY;
 
   rc = regcomp(&preg, (char *)pbuffer8, cflags);
-  if (rc != 0)   /* Failure */
+
+  /* Compiling failed */
+
+  if (rc != 0)
     {
     size_t bsize, usize;
 
@@ -4735,6 +4737,29 @@ if ((pat_patctl.control & CTL_POSIX) != 0)
       }
     return PR_SKIP;
     }
+
+  /* Compiling succeeded. Check that the values in the preg block are sensible.
+  It can happen that pcre2test is accidentally linked with a different POSIX
+  library which succeeds, but of course puts different things into preg. In
+  this situation, calling regfree() may cause a segfault (or invalid free() in
+  valgrind), so ensure that preg.re_pcre2_code is NULL, which suppresses the
+  calling of regfree() on exit. */
+
+  if (preg.re_pcre2_code == NULL ||
+      ((pcre2_real_code_8 *)preg.re_pcre2_code)->magic_number != MAGIC_NUMBER ||
+      ((pcre2_real_code_8 *)preg.re_pcre2_code)->top_bracket != preg.re_nsub ||
+      preg.re_match_data == NULL ||
+      preg.re_cflags != cflags)
+    {
+    fprintf(outfile,
+      "** The regcomp() function returned zero (success), but the values set\n"
+      "** in the preg block are not valid for PCRE2. Check that pcre2test is\n"
+      "** linked with PCRE2's pcre2posix module (-lpcre2-posix) and not with\n"
+      "** some other POSIX regex library.\n**\n");
+    preg.re_pcre2_code = NULL;
+    return PR_ABEND;
+    }
+
   return PR_OK;
 #endif  /* SUPPORT_PCRE2_8 */
   }
@@ -7450,7 +7475,7 @@ if (jit_stack != NULL)
 #ifdef SUPPORT_PCRE2_8
 #undef BITS
 #define BITS 8
-regfree(&preg);
+if (preg.re_pcre2_code != NULL) regfree(&preg);
 FREECONTEXTS;
 #endif