Address compiler and valgrind/sanitizer warnings

[PhilMiller]

I want to enable -Werror on the top-level ngen CI workflows. That requires that the formulation modules that we integration test build cleanly.

Changes

• Error check file read operations fgets() and fscanf()
• Return BMI_FAILURE on errors rather than exit()ing
• Check for BMI_FAILURE up the Initialize() call stack
• Add -Werror to compiler flags
• Pin OS versions in CI so that -Werror doesn't unexpectedly change meaning
• Initialize a variable that later gets printed
• Free the BMI object in the test driver to avoid a leak report

Testing

Github CI

Screenshots

Warnings seen in ngen Github CI:

/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c: In function ‘read_init_config’:
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:191:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  191 |     fscanf(model->control_fptr,"%d\n",&model->stand_alone);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:194:5: error: ignoring return value of ‘fgets’, declared with attribute warn_unused_result [-Werror=unused-result]
  194 |     fgets(model->title,256,model->control_fptr);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:200:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  200 |     fscanf(model->control_fptr,"%s",input_fname);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:211:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  211 |     fscanf(model->control_fptr,"%s",subcat_fname);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:212:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  212 |     fscanf(model->control_fptr,"%s",params_fname);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:215:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  215 |     fscanf(model->control_fptr,"%s",output_fname);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:216:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  216 |     fscanf(model->control_fptr,"%s",out_hyd_fname);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/home/runner/work/ngen/ngen/extern/topmodel/topmodel/src/bmi_topmodel.c:235:5: error: ignoring return value of ‘fscanf’, declared with attribute warn_unused_result [-Werror=unused-result]
  235 |     fscanf(model->subcat_fptr,"%d %d %d",&model->num_sub_catchments,&model->imap,&model->yes_print_output);
      |     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors

Checklist

• PR has an informative and human-readable title
• Changes are limited to a single goal (no scope creep)
• Code can be automatically merged (no conflicts)
• Code follows project standards (link if applicable)
• Passes all existing automated tests
• Any change in functionality is tested
• New functions are documented (with a description, list of inputs, and expected output)
• Placeholder code is flagged / future todos are captured in comments
• Visually tested in supported browsers and devices (see checklist below 👇)
• Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• Reviewers requested with the Reviewers tool ➡️

Testing checklist

Target Environment support

• Linux
• macOS

[aaraney]

This looks great! Thanks, @PhilMiller for making these improvements!

Just an acknowledgment review.