Improve CCUtil::main_setup (fixes issue tesseract-ocr#4230)

Conda installations patch TESSDATA_PREFIX in the binary.
That does not work for std::string because the length
won't be patched, so use a normal C string which can be
patched.

Simplify also the code which checks the last character
of datadir.

Signed-off-by: Stefan Weil <[email protected]>

src/ccutil/ccutil.cpp

@@ -46,7 +46,7 @@ CCUtil::~CCUtil() = default;
 void CCUtil::main_setup(const std::string &argv0, const std::string &basename) {
  imagebasename = basename; /**< name of image */
 
- char *tessdata_prefix = getenv("TESSDATA_PREFIX");
+ const char *tessdata_prefix = getenv("TESSDATA_PREFIX");
 
  if (!argv0.empty()) {
  /* Use tessdata prefix from the command line. */
@@ -77,17 +77,20 @@ void CCUtil::main_setup(const std::string &argv0, const std::string &basename) {
  if (datadir.empty()) {
 #if defined(TESSDATA_PREFIX)
  // Use tessdata prefix which was compiled in.
- datadir = TESSDATA_PREFIX "/tessdata";
+ // Note that some software (for example conda) patch TESSDATA_PREFIX
+ // in the binary, so it should not be used directly with a std::string.
+ tessdata_prefix = TESSDATA_PREFIX;
+ datadir = tessdata_prefix;
+ datadir += "/tessdata/";
 #else
  datadir = "./";
 #endif /* TESSDATA_PREFIX */
  }
 
  // check for missing directory separator
- const char *lastchar = datadir.c_str();
- lastchar += datadir.length() - 1;
- if ((strcmp(lastchar, "/") != 0) && (strcmp(lastchar, "\\") != 0)) {
- datadir += "/";
+ const char lastchar = datadir.back();
+ if (lastchar != '/' && lastchar != '\\') {
+ datadir += '/';
  }
 }