Program to reproduce the PCRE JIT Valgrind warning

test.c

#include <stdio.h>
#include <string.h>
#include "pcre.h"

int main(void) {
    pcre_extra *sd;
    pcre       *re;
    const char *errstr;
    int         erroff, rc;
    const char *ver = pcre_version(); 
    char *reg = strdup("b");
    char *sub = strdup("a");

    fprintf(stderr, "running: %s\n", ver);

    re = pcre_compile(reg, 0, &errstr, &erroff, NULL);
    if (!re) {
        fprintf(stderr, "pcre_compile() failed");
        return 1;
    }

    sd = pcre_study(re, PCRE_STUDY_JIT_COMPILE, &errstr);
    if (!sd || errstr) {
        fprintf(stderr, "pcre_study() failed");
        return 1;
    }

    rc = pcre_exec(re, sd, sub, 1, 0, 0, NULL,
                   0);
    if (rc != PCRE_ERROR_NOMATCH) {
        fprintf(stderr, "pcre_exec() failed: %d\n", rc);
    }

    pcre_free_study(sd);
    pcre_free(re);
    free(reg);
    free(sub);

    return 0;
}

The result is:

$ ./configure --enable-jit --prefix=$HOME/pcre-8.4-build --enable-valgrind
$ make -j4 && make install
$ cd $HOME/pcre-8.4-build/lib
$ gcc -g test.c libpcre.a
$ valgrind ./a.out 
==11428== Memcheck, a memory error detector
==11428== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==11428== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==11428== Command: ./a.out
==11428== 
running: 8.40 2017-01-11
==11428== Invalid read of size 16
==11428==    at 0x4C1307B: ???
==11428==    by 0x4C2E08F: ???
==11428==    by 0xFFEFF7D2F: ???
==11428==  Address 0x4c2e090 is 0 bytes inside a block of size 2 alloc'd
==11428==    at 0x4A06C50: malloc (in /usr/lib64/valgrind/vgpreload_memcheck-amd64-linux.so)
==11428==    by 0x3E61E8B079: strdup (in /usr/lib64/libc-2.21.so)
==11428==    by 0x400C2E: main (test.c:12)
==11428== 
==11428== 
==11428== HEAP SUMMARY:
==11428==     in use at exit: 0 bytes in 0 blocks
==11428==   total heap usage: 10 allocs, 10 frees, 8,634 bytes allocated
==11428== 
==11428== All heap blocks were freed -- no leaks are possible
==11428== 
==11428== For counts of detected and suppressed errors, rerun with: -v
==11428== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)