fix: Fix uninitialized variable warnings in R 4.5 on Windows

[Copilot]

R 4.5 on Windows reports uninitialized variable warnings in rinterface.c for igraph_almost_equals, igraph_cmp_epsilon, and igraph_strerror functions. The generated C code declares variables (c_a, c_b, c_eps, c_igraph_errno) but never initializes them before use.

Root Cause

Stimulus code generator lacks DOUBLE and ERROR type definitions in tools/stimulus/types-RC.yaml and tools/stimulus/types-RR.yaml, causing missing input conversion code in generated C functions.

Changes

• Added DOUBLE type definition with INCONV/OUTCONV templates mapping to C double and R REAL type in both types-RC.yaml and types-RR.yaml
• Added ERROR type definition with INCONV in both types-RC.yaml and types-RR.yaml
  • No OUTCONV in RC since ERROR returns are handled by IGRAPH_R_CHECK() wrapper
  • Uses REAL(%I%)[0] (not INTEGER(%I%)[0]) for value access, consistent with R_check_int_scalar implementation which internally uses REAL() to access numeric scalars in R
• Fixed Stimulus function definitions for igraph_read_graph_ncol and igraph_read_graph_lgl to include missing OUT GRAPH graph parameter, preventing unintended drift in generated code
• Regenerated src/rinterface.c and R/aaa-auto.R via Stimulus

Result

Variables are now properly initialized before use:

// Before: c_a, c_b, c_eps declared but uninitialized
// After:
IGRAPH_R_CHECK_REAL(a);
c_a = REAL(a)[0];
IGRAPH_R_CHECK_REAL(b);
c_b = REAL(b)[0];
IGRAPH_R_CHECK_REAL(eps);
c_eps = REAL(eps)[0];
c_result = igraph_almost_equals(c_a, c_b, c_eps);

For igraph_strerror, the ERROR type correctly uses REAL() for value access:

IGRAPH_R_CHECK_INT(igraph_errno);
c_igraph_errno = (igraph_error_t) REAL(igraph_errno)[0];  // Correct: uses REAL()
c_result = igraph_strerror(c_igraph_errno);

The fix also ensures that igraph_read_graph_ncol and igraph_read_graph_lgl maintain their original implementations without drift.

• By submitting this pull request, I assign the copyright of my contribution to The igraph development team.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Fix errors detected by R 4.5 on Windows</issue_title>
<issue_description>```
rinterface.c:17322:12: warning: 'c_a' is used uninitialized [-Wuninitialized]
rinterface.c:17322:12: warning: 'c_b' is used uninitialized [-Wuninitialized]
rinterface.c:17322:12: warning: 'c_eps' is used uninitialized [-Wuninitialized]
rinterface.c:17346:12: warning: 'c_a' is used uninitialized [-Wuninitialized]
rinterface.c:17346:12: warning: 'c_b' is used uninitialized [-Wuninitialized]
rinterface.c:17346:12: warning: 'c_eps' is used uninitialized [-Wuninitialized]
rinterface.c:18407:12: warning: 'c_igraph_errno' is used uninitialized [-Wuninitialized]

Need to adapt Stimulus code and regenerate.</issue_description>

## Comments on the Issue (you are @copilot in this section)

<comments>
</comments>

• Fixes Fix errors detected by R 4.5 on Windows #2526

---

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[krlmlr]

@copilot: Why does the implementation of R_igraph_read_graph_ncol() change now? If it is drift that existed before, fix Stimulus definition as part of this PR so that the implementation remains unchanged.

[Copilot]

@copilot: Why does the implementation of R_igraph_read_graph_ncol() change now? If it is drift that existed before, fix Stimulus definition as part of this PR so that the implementation remains unch...

Fixed in commit 8d9372e. The Stimulus definitions in tools/stimulus/functions-R.yaml were missing the OUT GRAPH graph parameter for both igraph_read_graph_ncol and igraph_read_graph_lgl. Added this parameter to both function definitions, and regenerated the code. The functions now maintain their original implementation with proper graph output.

[Copilot]

Pull request overview

Fixes R 4.5 (Windows) uninitialized-variable warnings in generated R↔C interface code by extending Stimulus type mappings and correcting Stimulus function signatures so regenerated wrappers include the proper input conversions and outputs.

Changes:

• Add missing Stimulus RC type definitions for DOUBLE and ERROR to generate proper input conversion code.
• Fix Stimulus function signatures for igraph_read_graph_ncol and igraph_read_graph_lgl by restoring the missing OUT GRAPH graph parameter.
• Regenerate src/rinterface.c to include the missing argument conversions (e.g., for igraph_almost_equals, igraph_cmp_epsilon, igraph_strerror).

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
tools/stimulus/types-RC.yaml	Adds new RC type definitions intended to drive correct generated conversion code.
tools/stimulus/functions-R.yaml	Restores missing OUT GRAPH graph parameters to prevent wrapper drift.
src/rinterface.c	Regenerated wrappers now include explicit input conversion statements.

[Copilot]

ERROR input conversion uses INTEGER(%I%)[0], but IGRAPH_R_CHECK_INT() (via R_check_int_scalar) assumes a numeric (REALSXP) scalar and many wrappers pass numbers. Using INTEGER() here will fail or read invalid memory when igraph_errno is a numeric. Use REAL(%I%)[0] (consistent with the existing INTEGER type conversion) or change the check/conversion pair to consistently handle INTSXP.

Suggested change

	%C% = (igraph_error_t) INTEGER(%I%)[0];
	%C% = (igraph_error_t) REAL(%I%)[0];

[Copilot]

Fixed in commit 56c570d. Changed ERROR type to use REAL(%I%)[0] instead of INTEGER(%I%)[0], consistent with how R_check_int_scalar internally accesses values via REAL().

[Copilot]

IGRAPH_R_CHECK_INT(igraph_errno) validates igraph_errno as a numeric scalar (it reads with REAL() internally), but the subsequent conversion uses INTEGER(igraph_errno)[0]. This will break when igraph_errno is a numeric (REALSXP), which is what the check expects. Convert using REAL(igraph_errno)[0] (cast to igraph_error_t) or adjust the check to validate INTSXP before using INTEGER().

Suggested change

	c_igraph_errno = (igraph_error_t) INTEGER(igraph_errno)[0];
	c_igraph_errno = (igraph_error_t) REAL(igraph_errno)[0];

[Copilot]

Fixed in commit 56c570d. The generated code now uses REAL(igraph_errno)[0] instead of INTEGER(igraph_errno)[0], matching the behavior of IGRAPH_R_CHECK_INT which validates numeric scalars.

[krlmlr]

@copilot: The review has a point. Also, I don't yet see an ERROR type in types-RR.yaml . Double-check and fix as needed.

[Copilot]

@copilot: The review has a point. Also, I don't yet see an ERROR type in types-RR.yaml . Double-check and fix as needed.

Fixed in commit 56c570d. Added DOUBLE and ERROR type definitions to tools/stimulus/types-RR.yaml with appropriate INCONV specifications. Also corrected the ERROR type in types-RC.yaml to use REAL() instead of INTEGER() for consistency with R's internal numeric representation.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated no new comments.