Add a plain build variant

This is essentially a glorified (ctx << 32 | errno). Why one might use
this build variant though is to keep the same error code generation call
sites even if the compiler doesn't support the pre-requisite features
for the full merr. Alternatively, a library may have too many source
files, in which case merr would return garbage most likely. What that
upper limit on source files is yet to be discovered.

.github/workflows/builds.yaml

@@ -38,23 +38,25 @@ concurrency:
 jobs:
   normal:
     runs-on: ubuntu-latest
+    container: quay.io/fedora/fedora:38
     strategy:
       fail-fast: true
       matrix:
         buildtype: [debug, release]
+        plain: [enabled, disabled]
 
     steps:
       - name: Install dependencies
         run: |
-          sudo apt-get install -y meson
+          dnf install --assumeyes gcc meson
 
       - name: Checkout libmerr
         uses: actions/checkout@v3
 
       - name: Setup
         run: |
           meson setup build --fatal-meson-warnings --werror \
-            --buildtype=${{ matrix.buildtype }}
+            --buildtype=${{ matrix.buildtype }} -Dplain=${{ matrix.plain }}
 
       - name: Build
         run: |
@@ -66,23 +68,26 @@ jobs:
 
   asan-ubsan:
     runs-on: ubuntu-latest
+    container: quay.io/fedora/fedora:38
     strategy:
       fail-fast: true
       matrix:
         buildtype: [debug, release]
+        plain: [enabled, disabled]
 
     steps:
       - name: Install dependencies
         run: |
-          sudo apt-get install -y meson
+          dnf install --assumeyes gcc meson libasan libubsan
 
       - name: Checkout libmerr
         uses: actions/checkout@v3
 
       - name: Setup
         run: |
           meson setup build --fatal-meson-warnings --werror \
-            --buildtype=${{ matrix.buildtype }} -Db_sanitize=address,undefined
+            --buildtype=${{ matrix.buildtype }} -Db_sanitize=address,undefined \
+            -Dplain=${{ matrix.plain }}
 
       - name: Build
         run: |

.github/workflows/codeql.yaml

@@ -33,11 +33,12 @@ permissions:
 jobs:
   codeql:
     runs-on: ubuntu-latest
+    container: quay.io/fedora/fedora:38
 
     steps:
       - name: Install dependencies
         run: |
-          sudo apt-get install -y meson
+          sudo apt-get install -y gcc meson
 
       - name: Checkout libmerr
         uses: actions/checkout@v3

include/merr.h

@@ -15,15 +15,7 @@ extern "C" {
 #include <stdint.h>
 
 #ifndef __has_attribute
-#error "__has_attribute must be provided by the compiler"
-#endif
-
-#if !__has_attribute(aligned)
-#error "Copmiler must support the aligned attribute"
-#endif
-
-#if !__has_attribute(section)
-#error "Compiler must support the section attribute"
+#define __has_attribute(_attr) 0
 #endif
 
 #if __has_attribute(always_inline)
@@ -50,23 +42,39 @@ extern "C" {
 #define MERR_WARN_UNUSED_RESULT
 #endif
 
+#ifndef MERR_PLAIN
 // Alignment of merr_curr_file in section "merr"
 #define MERR_MAX_PATH_LENGTH (1 << 6)
-
 #define merr_attributes __attribute__((section("merr"))) __attribute__((aligned(MERR_MAX_PATH_LENGTH)))
 
 static char merr_curr_file[MERR_MAX_PATH_LENGTH] merr_attributes MERR_USED = __BASE_FILE__;
 
+#endif
+
+
 /* Layout of merr_t:
  *
- *   Field   #bits  Description
- *   ------  -----  ----------
- *   63..48   16    signed offset of (merr_curr_file - merr_base) / MERR_MAX_PATH_LENGTH
- *   47..32   16    line number
- *   31..16   16    context
- *   15..0    16    error value
+ *   If the compiler supports both the section and aligned attributes and
+ *   MERR_PLAIN was not requested:
+ *
+ *     Field   #bits  Description
+ *     ------  -----  ----------
+ *     63..48   16    signed offset of (merr_curr_file - merr_base) / MERR_MAX_PATH_LENGTH
+ *     47..32   16    line number
+ *     31..16   16    context
+ *     15..0    16    error value
+ *
+ *   If the compiler does not support either of the section or aligned
+ *   attributes, or MERR_PLAIN was requested:
+ *
+ *     Field   #bits  Description
+ *     ------  -----  ----------
+ *     63..32   32    context
+ *     31..0    32    error value
  */
 
+#ifndef MERR_PLAIN
+
 #define MERR_FILE_SHIFT 48
 #define MERR_LINE_SHIFT 32
 #define MERR_CTX_SHIFT  16
@@ -76,6 +84,18 @@ static char merr_curr_file[MERR_MAX_PATH_LENGTH] merr_attributes MERR_USED = __B
 #define MERR_CTX_MASK   0x00000000ffff0000LL
 #define MERR_ERRNO_MASK 0x000000000000ffffLL
 
+#define MERR_CTX_TYPE int16_t
+
+#else
+
+#define MERR_CTX_SHIFT  32
+
+#define MERR_ERRNO_MASK 0x00000000ffffffffLL
+
+#define MERR_CTX_TYPE int32_t
+
+#endif
+
 /**
  * @brief The error value type.
  */
@@ -108,6 +128,8 @@ merr_stringify(int num);
  */
 #define merr(_errnum) merrx((_errnum), 0)
 
+#ifndef MERR_PLAIN
+
 /**
  * @brief Pack given error number, call-site info, and context into an merr_t.
  *
@@ -117,16 +139,33 @@ merr_stringify(int num);
  */
 #define merrx(_errnum, _ctx) merr_pack((_errnum), (_ctx), merr_curr_file, __LINE__)
 
+#else
+
+/**
+ * @brief Pack given error number and context into an merr_t.
+ *
+ * @param _errnum Error number.
+ * @param _ctx Context.
+ * @returns An merr_t.
+ */
+#define merrx(_errnum, _ctx) merr_pack((_errnum), (_ctx))
+
+#endif
+
 /**
  * @brief Get the context.
  *
  * @param err Error.
  * @returns Error context.
  */
-static MERR_ALWAYS_INLINE int16_t MERR_CONST MERR_USED MERR_WARN_UNUSED_RESULT
+static MERR_ALWAYS_INLINE MERR_CTX_TYPE MERR_CONST MERR_USED MERR_WARN_UNUSED_RESULT
 merr_ctx(const merr_t err)
 {
-    return (int16_t)((err & MERR_CTX_MASK) >> MERR_CTX_SHIFT);
+#ifndef MERR_PLAIN
+    return (MERR_CTX_TYPE)((err & MERR_CTX_MASK) >> MERR_CTX_SHIFT);
+#else
+    return (MERR_CTX_TYPE)(err >> MERR_CTX_SHIFT);
+#endif
 }
 
 /**
@@ -138,9 +177,11 @@ merr_ctx(const merr_t err)
 static MERR_ALWAYS_INLINE int MERR_CONST MERR_USED MERR_WARN_UNUSED_RESULT
 merr_errno(const merr_t err)
 {
-    return err & MERR_ERRNO_MASK;
+    return (int)(err & MERR_ERRNO_MASK);
 }
 
+#ifndef MERR_PLAIN
+
 /**
  * @brief Get the file name the error was generated in.
  *
@@ -165,6 +206,8 @@ merr_lineno(const merr_t err)
     return (uint16_t)((err & MERR_LINE_MASK) >> MERR_LINE_SHIFT);
 }
 
+#endif
+
 /**
  * @brief Format file, line, ctx, and errno from an merr_t into a buffer.
  *
@@ -187,10 +230,20 @@ merr_strerrorx(merr_t err, char *buf, size_t buf_sz, merr_stringify ctx_stringif
  */
 #define merr_strerror(_err, _buf, _buf_sz) merr_strerrorx((_err), (_buf), (_buf_sz), NULL)
 
+#ifndef MERR_PLAIN
+
 // This is not public API. DO NOT USE.
 merr_t
 merr_pack(int errnum, int ctx, const char *file, uint16_t line) MERR_CONST MERR_WARN_UNUSED_RESULT;
 
+#else
+
+// This is not public API. DO NOT USE.
+merr_t
+merr_pack(int errnum, int ctx) MERR_CONST MERR_WARN_UNUSED_RESULT;
+
+#endif
+
 #ifdef __cplusplus
 }
 #endif

lib/merr.c

@@ -20,13 +20,15 @@
 #define MERR_UNUSED
 #endif
 
+#ifndef MERR_PLAIN
 char merr_base[MERR_MAX_PATH_LENGTH] merr_attributes = "merr_base";
 char merr_bug0[MERR_MAX_PATH_LENGTH] merr_attributes = "merr_bug0";
 char merr_bug1[MERR_MAX_PATH_LENGTH] merr_attributes = "merr_bug1";
 char merr_bug2[MERR_MAX_PATH_LENGTH] merr_attributes = "merr_bug2";
 
 extern uint8_t __start_merr;
 extern uint8_t __stop_merr;
+#endif
 
 #ifndef HAVE_STRLCPY
 
@@ -54,6 +56,8 @@ strlcpy(char * const dst, const char * const src, const size_t sz)
 
 #endif
 
+#ifndef MERR_PLAIN
+
 const char *
 merr_file(const merr_t err)
 {
@@ -114,6 +118,27 @@ merr_pack(const int errnum, const int ctx, const char *file, const uint16_t line
     return err;
 }
 
+#else
+
+merr_t
+merr_pack(const int errnum, const int ctx)
+{
+    merr_t err = 0;
+
+    if (errnum == 0)
+        return 0;
+
+    if (errnum < INT32_MIN || errnum > INT32_MAX || ctx < INT32_MIN || ctx > INT32_MAX)
+        return merr(EINVAL);
+
+    err |= ((int64_t)ctx << MERR_CTX_SHIFT);
+    err |= (int64_t)errnum & MERR_ERRNO_MASK;
+
+    return err;
+}
+
+#endif
+
 static size_t
 strerror_safe(const merr_t err, char * const buf, const size_t buf_sz)
 {
@@ -138,33 +163,38 @@ size_t
 merr_strerrorx(const merr_t err, char * const buf, size_t buf_sz, merr_stringify ctx_stringify)
 {
     int ret;
-    int16_t ctx;
     size_t sz = 0;
-    const char *file;
+    MERR_CTX_TYPE ctx;
 
     if (!buf && buf_sz > 0)
         buf_sz = 0;
 
     if (!err)
         return strlcpy(buf, "Success", buf_sz);
 
-    file = merr_file(err);
-    if (file) {
-        const char *ptr;
+#ifndef MERR_PLAIN
+    {
+        const char *file;
 
-        // Protect against files that may be too long.
-        ptr = memchr(file, '\0', MERR_MAX_PATH_LENGTH);
-        ret = snprintf(
-            buf, buf_sz, "%*s:%d: ", (int)(ptr ? ptr - file : MERR_MAX_PATH_LENGTH), file,
-            merr_lineno(err));
+        file = merr_file(err);
+        if (file) {
+            const char *ptr;
 
-        if (ret < 0) {
-            sz = strlcpy(buf, "<failed to format the error message>", buf_sz);
-            goto out;
-        }
+            // Protect against files that may be too long.
+            ptr = memchr(file, '\0', MERR_MAX_PATH_LENGTH);
+            ret = snprintf(
+                buf, buf_sz, "%*s:%d: ", (int)(ptr ? ptr - file : MERR_MAX_PATH_LENGTH), file,
+                merr_lineno(err));
 
-        sz += (size_t)ret;
+            if (ret < 0) {
+                sz = strlcpy(buf, "<failed to format the error message>", buf_sz);
+                goto out;
+            }
+
+            sz += (size_t)ret;
+        }
     }
+#endif
 
     if (sz >= buf_sz) {
         sz += strerror_safe(err, NULL, 0);

lib/meson.build

@@ -11,9 +11,22 @@ configure_file(
     }
 )
 
+cc_has_aligned = cc.has_function_attribute('aligned')
+cc_has_section = cc.has_function_attribute('section')
+if get_option('plain').disabled() and (not cc_has_aligned or not cc_has_section)
+    error('Compiler must support both aligned' +
+        ' and section attributes if -Dplain=disabled')
+endif
+
+c_args = []
+if get_option('plain').enabled() or not cc_has_aligned or not cc_has_section
+    c_args += '-DMERR_PLAIN'
+endif
+
 libmerr = static_library(
     'merr',
     'merr.c',
+    c_args: c_args,
     include_directories: libmerr_includes,
     install: true,
     gnu_symbol_visibility: 'hidden'
@@ -25,6 +38,7 @@ variables = {
 }
 
 libmerr_dep = declare_dependency(
+    compile_args: c_args,
     link_with: libmerr,
     include_directories: libmerr_includes,
     variables: variables
@@ -38,6 +52,7 @@ if pkg.found()
         name: meson.project_name(),
         description: 'C99+ library for error information',
         url: 'https://github.com/tristan957/libmerr',
+        extra_cflags: c_args,
         variables: variables
     )
 endif

meson.build

@@ -13,7 +13,7 @@ project(
         'c_std=c99',
         'warning_level=3',
     ],
-    meson_version: '>= 0.59.0'
+    meson_version: '>= 0.63.0'
 )
 
 fs = import('fs', required: get_option('tests'))