Fix empty vs. unset environment variables on Windows.#1997
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BillyONeal wants to merge 4 commits intomicrosoft:mainfrom
Open
Fix empty vs. unset environment variables on Windows.#1997BillyONeal wants to merge 4 commits intomicrosoft:mainfrom
BillyONeal wants to merge 4 commits intomicrosoft:mainfrom
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This is a followup to microsoft#1988 where I observe that the same type of defect applies to the "normal" way vcpkg gets environment variables. Ensure that this is preserved correctly, enable use of the small string optimization for wstring, and audit all callers.
BillyONeal
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Pull request overview
Note
Copilot was unable to run its full agentic suite in this review.
This PR fixes Windows environment-variable handling to distinguish empty values from missing variables, improves the Win32 read path to better leverage std::wstring small-string optimization, and updates call sites accordingly.
Changes:
- Reworked Windows
get_environment_variable()to correctly return""vsnulloptand avoid extra Win32 API calls in common cases. - Added
get_environment_variable_nonempty()and updated selected callers to treat empty-as-missing where appropriate. - Added/adjusted tests to validate env-var roundtrips and SSO-sized reads.
Reviewed changes
Copilot reviewed 11 out of 11 changed files in this pull request and generated 8 comments.
Show a summary per file
| File | Description |
|---|---|
| src/vcpkg/visualstudio.cpp | Treat empty COMNTOOLS as absent and move the string into Path. |
| src/vcpkg/vcpkgcmdarguments.cpp | Adjust env-var retrieval for recursive JSON state parsing. |
| src/vcpkg/commands.integrate.cpp | Switch several uses of $HOME / XDG vars to “nonempty” semantics. |
| src/vcpkg/commands.edit.cpp | Treat empty editor/AppData vars as absent and move strings into paths. |
| src/vcpkg/commands.build.cpp | Refactor env-var lookups; use nonempty proxy env vars. |
| src/vcpkg/binarycaching.cpp | Use nonempty default cache path; tighten GitHub env-var handling. |
| src/vcpkg/base/system.cpp | Implement correct empty vs missing on Windows; add get_environment_variable_nonempty(); update path helpers. |
| src/vcpkg/base/files.cpp | Require nonempty PATH and TMPDIR where used. |
| src/vcpkg-test/util.cpp | Use the new nonempty env-var helper for TEMP. |
| src/vcpkg-test/system.cpp | Add env-var roundtrip tests; tweak test naming. |
| include/vcpkg/base/system.h | Declare get_environment_variable_nonempty(). |
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
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This is a followup to #1988 where I observe that the same type of defect applies to the "normal" way vcpkg gets environment variables.
Ensure that empty vs. unset is preserved correctly, enable use of the small string optimization for wstring, and audit all callers.