Merge pull request #9508 from infinisil/revert-7762-boost-regex

Revert "Switch from std::regex to boost::regex"

src/libexpr/local.mk

@@ -16,7 +16,7 @@ libexpr_CXXFLAGS += -I src/libutil -I src/libstore -I src/libfetchers -I src/lib
 
 libexpr_LIBS = libutil libstore libfetchers
 
-libexpr_LDFLAGS += -lboost_context -lboost_regex -pthread
+libexpr_LDFLAGS += -lboost_context -pthread
 ifdef HOST_LINUX
  libexpr_LDFLAGS += -ldl
 endif

src/libexpr/primops.cc

@@ -17,7 +17,6 @@
 #include "primops.hh"
 
 #include <boost/container/small_vector.hpp>
-#include <boost/regex.hpp>
 #include <nlohmann/json.hpp>
 
 #include <sys/types.h>
@@ -26,6 +25,7 @@
 
 #include <algorithm>
 #include <cstring>
+#include <regex>
 #include <dlfcn.h>
 
 #include <cmath>
@@ -3886,30 +3886,19 @@ static RegisterPrimOp primop_convertHash({
     .fun = prim_convertHash,
 });
 
-// regex aliases, switch between boost and std
-using regex = boost::regex;
-using regex_error = boost::regex_error;
-using cmatch = boost::cmatch;
-using cregex_iterator = boost::cregex_iterator;
-namespace regex_constants = boost::regex_constants;
-// overloaded function alias
-constexpr auto regex_match = [] (auto &&...args) {
-    return boost::regex_match(std::forward<decltype(args)>(args)...);
- };
-
 struct RegexCache
 {
     // TODO use C++20 transparent comparison when available
-    std::unordered_map<std::string_view, regex> cache;
+    std::unordered_map<std::string_view, std::regex> cache;
     std::list<std::string> keys;
 
-    regex get(std::string_view re)
+    std::regex get(std::string_view re)
     {
         auto it = cache.find(re);
         if (it != cache.end())
             return it->second;
         keys.emplace_back(re);
-        return cache.emplace(keys.back(), regex(keys.back(), regex::extended)).first->second;
+        return cache.emplace(keys.back(), std::regex(keys.back(), std::regex::extended)).first->second;
     }
 };
 
@@ -3929,8 +3918,8 @@ void prim_match(EvalState & state, const PosIdx pos, Value * * args, Value & v)
         NixStringContext context;
         const auto str = state.forceString(*args[1], context, pos, "while evaluating the second argument passed to builtins.match");
 
-        cmatch match;
-        if (!regex_match(str.begin(), str.end(), match, regex)) {
+        std::cmatch match;
+        if (!std::regex_match(str.begin(), str.end(), match, regex)) {
             v.mkNull();
             return;
         }
@@ -3945,8 +3934,8 @@ void prim_match(EvalState & state, const PosIdx pos, Value * * args, Value & v)
                 (v.listElems()[i] = state.allocValue())->mkString(match[i + 1].str());
         }
 
-    } catch (regex_error & e) {
-        if (e.code() == regex_constants::error_space) {
+    } catch (std::regex_error & e) {
+        if (e.code() == std::regex_constants::error_space) {
             // limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
             state.debugThrowLastTrace(EvalError({
                 .msg = hintfmt("memory limit exceeded by regular expression '%s'", re),
@@ -4009,8 +3998,8 @@ void prim_split(EvalState & state, const PosIdx pos, Value * * args, Value & v)
         NixStringContext context;
         const auto str = state.forceString(*args[1], context, pos, "while evaluating the second argument passed to builtins.split");
 
-        auto begin = cregex_iterator(str.begin(), str.end(), regex);
-        auto end = cregex_iterator();
+        auto begin = std::cregex_iterator(str.begin(), str.end(), regex);
+        auto end = std::cregex_iterator();
 
         // Any matches results are surrounded by non-matching results.
         const size_t len = std::distance(begin, end);
@@ -4049,8 +4038,8 @@ void prim_split(EvalState & state, const PosIdx pos, Value * * args, Value & v)
 
         assert(idx == 2 * len + 1);
 
-    } catch (regex_error & e) {
-        if (e.code() == regex_constants::error_space) {
+    } catch (std::regex_error & e) {
+        if (e.code() == std::regex_constants::error_space) {
             // limit is _GLIBCXX_REGEX_STATE_LIMIT for libstdc++
             state.debugThrowLastTrace(EvalError({
                 .msg = hintfmt("memory limit exceeded by regular expression '%s'", re),

src/libexpr/tests/primops.cc

@@ -814,6 +814,14 @@ namespace nix {
         ASSERT_THAT(*v.listElems()[0], IsStringEq("FOO"));
     }
 
+    TEST_F(PrimOpTest, match5) {
+        // The regex "\\{}" is valid and matches the string "{}".
+        // Caused a regression before when trying to switch from std::regex to boost::regex.
+        // See https://github.com/NixOS/nix/pull/7762#issuecomment-1834303659
+        auto v = eval("builtins.match \"\\\\{}\" \"{}\"");
+        ASSERT_THAT(v, IsListOfSize(0));
+    }
+
     TEST_F(PrimOpTest, attrNames) {
         auto v = eval("builtins.attrNames { x = 1; y = 2; z = 3; a = 2; }");
         ASSERT_THAT(v, IsListOfSize(4));