C API: Keep the structure flat

See https://github.com/NixOS/nix/pull/10329

Makefile

@@ -18,9 +18,9 @@ makefiles = \
   src/libexpr/local.mk \
   src/libcmd/local.mk \
   src/nix/local.mk \
-  src/libutil/c/local.mk \
-  src/libstore/c/local.mk \
-  src/libexpr/c/local.mk \
+  src/libutil-c/local.mk \
+  src/libstore-c/local.mk \
+  src/libexpr-c/local.mk \
   src/resolve-system-dependencies/local.mk \
   scripts/local.mk \
   misc/bash/local.mk \

doc/external-api/doxygen.cfg.in

@@ -36,9 +36,9 @@ GENERATE_LATEX         = NO
 # so they can expand variables despite configure variables.
 
 INPUT                  = \
-  src/libutil/c \
-  src/libexpr/c \
-  src/libstore/c \
+  src/libutil-c \
+  src/libexpr-c \
+  src/libstore-c \
   doc/external-api/README.md
 
 FILE_PATTERNS = nix_api_*.h *.md

local.mk

@@ -2,7 +2,7 @@ GLOBAL_CXXFLAGS += -Wno-deprecated-declarations -Werror=switch
 # Allow switch-enum to be overridden for files that do not support it, usually because of dependency headers.
 ERROR_SWITCH_ENUM = -Werror=switch-enum
 
-$(foreach i, config.h $(wildcard src/lib*/*.hh) $(wildcard src/lib*/*.h $(filter-out %_internal.h, $(wildcard src/lib*/c/*.h))), \
+$(foreach i, config.h $(wildcard src/lib*/*.hh) $(wildcard src/lib*/*.h $(filter-out %_internal.h, $(wildcard src/lib*c/*.h))), \
   $(eval $(call install-file-in, $(i), $(includedir)/nix, 0644)))
 
 $(GCH): src/libutil/util.hh config.h

src/libexpr-c/local.mk

@@ -0,0 +1,25 @@
+libraries += libexprc
+
+libexprc_NAME = libnixexprc
+
+libexprc_DIR := $(d)
+
+libexprc_SOURCES := \
+  $(wildcard $(d)/*.cc) \
+
+# Not just for this library itself, but also for downstream libraries using this library
+
+INCLUDE_libexprc := -I $(d)
+libexprc_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libutilc) \
+                     $(INCLUDE_libfetchers) \
+                     $(INCLUDE_libstore) $(INCLUDE_libstorec) \
+                     $(INCLUDE_libexpr) $(INCLUDE_libexprc)
+
+libexprc_LIBS = libutil libutilc libstore libstorec libexpr
+
+libexprc_LDFLAGS += -pthread
+
+$(eval $(call install-file-in, $(d)/nix-expr-c.pc, $(libdir)/pkgconfig, 0644))
+
+libexprc_FORCE_INSTALL := 1
+

src/libexpr/c/local.mk

@@ -1,19 +0,0 @@
-libraries += libexprc
-
-libexprc_NAME = libnixexprc
-
-libexprc_DIR := $(d)
-
-libexprc_SOURCES := \
-  $(wildcard $(d)/*.cc) \
-
-libexprc_CXXFLAGS += -I src/libutil -Isrc/libfetchers -I src/libstore -I src/libstorec -I src/libexpr -I src/libutil/c -I src/libstore/c
-
-libexprc_LIBS = libutil libutilc libstore libstorec libexpr
-
-libexprc_LDFLAGS += -pthread
-
-$(eval $(call install-file-in, $(d)/nix-expr-c.pc, $(libdir)/pkgconfig, 0644))
-
-libexprc_FORCE_INSTALL := 1
-

src/libstore-c/local.mk

@@ -10,7 +10,11 @@ libstorec_LIBS = libutil libstore libutilc
 
 libstorec_LDFLAGS += -pthread
 
-libstorec_CXXFLAGS += -I src/libutil -I src/libstore -I src/libutil/c
+# Not just for this library itself, but also for downstream libraries using this library
+
+INCLUDE_libstorec := -I $(d)
+libstorec_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libutilc) \
+		    $(INCLUDE_libstore) $(INCLUDE_libstorec)
 
 $(eval $(call install-file-in, $(d)/nix-store-c.pc, $(libdir)/pkgconfig, 0644))
 

src/libutil-c/local.mk

@@ -6,7 +6,10 @@ libutilc_DIR := $(d)
 
 libutilc_SOURCES := $(wildcard $(d)/*.cc)
 
-libutilc_CXXFLAGS += -I src/libutil
+# Not just for this library itself, but also for downstream libraries using this library
+
+INCLUDE_libutilc := -I $(d)
+libutilc_CXXFLAGS += $(INCLUDE_libutil) $(INCLUDE_libutilc)
 
 libutilc_LIBS = libutil
 

tests/unit/libexpr/local.mk

@@ -24,9 +24,12 @@ libexpr-tests_EXTRA_INCLUDES = \
     -I tests/unit/libstore-support \
     -I tests/unit/libutil-support \
     $(INCLUDE_libexpr) \
+    $(INCLUDE_libexprc) \
     $(INCLUDE_libfetchers) \
     $(INCLUDE_libstore) \
-    $(INCLUDE_libutil)
+    $(INCLUDE_libstorec) \
+    $(INCLUDE_libutil) \
+    $(INCLUDE_libutilc)
 
 libexpr-tests_CXXFLAGS += $(libexpr-tests_EXTRA_INCLUDES)
 

tests/unit/libstore/local.mk

@@ -20,7 +20,9 @@ libstore-tests_EXTRA_INCLUDES = \
     -I tests/unit/libstore-support \
     -I tests/unit/libutil-support \
     $(INCLUDE_libstore) \
-    $(INCLUDE_libutil)
+    $(INCLUDE_libstorec) \
+    $(INCLUDE_libutil) \
+    $(INCLUDE_libutilc)
 
 libstore-tests_CXXFLAGS += $(libstore-tests_EXTRA_INCLUDES)
 

tests/unit/libutil/local.mk

@@ -18,7 +18,8 @@ libutil-tests_SOURCES := $(wildcard $(d)/*.cc)
 
 libutil-tests_EXTRA_INCLUDES = \
     -I tests/unit/libutil-support \
-    $(INCLUDE_libutil)
+    $(INCLUDE_libutil) \
+    $(INCLUDE_libutilc)
 
 libutil-tests_CXXFLAGS += $(libutil-tests_EXTRA_INCLUDES)
 

tests/unit/libutil/nix_api_util.cc

@@ -1,4 +1,3 @@
-
 #include "config.hh"
 #include "args.hh"
 #include "nix_api_util.h"