TessBaseAPIInit1() should take config file list as const

[M-Fabian]

Environment

• Tesseract Version: 4.0 and newer
• Commit Number:
• Platform: issue is independent of the platform

Current Behavior:

In the C API, the function int TessBaseAPIInit1() accepts a list of configuration files with the parameters char **configs, int configs_size. Although configs is used read-only, it is not correctly const-qualified, which is annoying for me as a user because I have to use const_cast.

char * configs[1];
configs[0] = const_cast<char *>(strConfigFile.c_str());
int r = TessBaseAPIInit1(h, strTessdata.c_str(), "eng", OEM_DEFAULT, configs, 1);

Expected Behavior:

TessBaseAPIInit1 should accept an array of const char pointers.

Suggested Fix:

Change the signature from
TESS_API int TessBaseAPIInit1(TessBaseAPI *handle, const char *datapath, const char *language, TessOcrEngineMode oem, char **configs, int configs_size);

to

TESS_API int TessBaseAPIInit1(TessBaseAPI *handle, const char *datapath, const char *language, TessOcrEngineMode oem, const char **configs, int configs_size);

The implementation is the same because the function does not modify the array of strings.

[stweil]

@M-Fabian, do you want to prepare a patch? It is not sufficient to change TessBaseAPIInit1. const has to be added to lots of other functions, too. Maybe it is not possible at all (at least not in a compatible way), because it breaks existing code which tries to pass a char **.